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 $87.59   8.172%   $94.7479   $94.75   $94.75   $94.70  
  Purchase #2 $83.52   7.531%   $89.8099   $89.81   $89.80   $89.80  
  Purchase #3 $55.81   5.865%   $59.0833   $59.08   $59.10   $59.10  
  Purchase #4 $26.36   10.707%   $29.1824   $29.18   $29.20   $29.20  
  Purchase #5 $158.64   9.457%   $173.6426   $173.64   $173.65   $173.60  
  Purchase #6 $68.58   8.242%   $74.2324   $74.23   $74.25   $74.20  
  Purchase #7 $38.67   12.710%   $43.585   $43.59   $43.60   $43.60  
  7 purchase totals = $519.17       $564.2835   $564.28   $564.35   $564.20