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 $173.44   7.711%   $186.814   $186.81   $186.80   $186.80  
  Purchase #2 $192.86   4.208%   $200.9755   $200.98   $201.00   $201.00  
  Purchase #3 $56.32   7.847%   $60.7394   $60.74   $60.75   $60.70  
  Purchase #4 $230.61   6.798%   $246.2869   $246.29   $246.30   $246.30  
  Purchase #5 $82.60   8.395%   $89.5343   $89.53   $89.55   $89.50  
  Purchase #6 $138.59   4.735%   $145.1522   $145.15   $145.15   $145.20  
  Purchase #7 $178.85   8.575%   $194.1864   $194.19   $194.20   $194.20  
  7 purchase totals = $1,053.27       $1,123.6887   $1,123.69   $1,123.75   $1,123.70