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 $214.41   10.840%   $237.652   $237.65   $237.65   $237.70  
  Purchase #2 $202.82   5.300%   $213.5695   $213.57   $213.55   $213.60  
  Purchase #3 $53.60   6.107%   $56.8734   $56.87   $56.85   $56.90  
  Purchase #4 $73.56   9.227%   $80.3474   $80.35   $80.35   $80.30  
  Purchase #5 $98.70   13.820%   $112.3403   $112.34   $112.35   $112.30  
  Purchase #6 $98.72   3.716%   $102.3884   $102.39   $102.40   $102.40  
  Purchase #7 $212.66   4.868%   $223.0123   $223.01   $223.00   $223.00  
  7 purchase totals = $954.47       $1,026.1833   $1,026.18   $1,026.15   $1,026.20