Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $80.92   8.132%   $87.5004   $87.50   $87.50   $87.50  
  Purchase #2 $179.33   8.714%   $194.9568   $194.96   $194.95   $195.00  
  Purchase #3 $122.29   12.414%   $137.4711   $137.47   $137.45   $137.50  
  Purchase #4 $228.94   8.731%   $248.9288   $248.93   $248.95   $248.90  
  Purchase #5 $193.36   5.378%   $203.7589   $203.76   $203.75   $203.80  
  Purchase #6 $112.53   11.803%   $125.8119   $125.81   $125.80   $125.80  
  Purchase #7 $109.43   5.611%   $115.5701   $115.57   $115.55   $115.60  
  7 purchase totals = $1,026.80       $1,113.9980   $1,114.00   $1,113.95   $1,114.10