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 $183.56   6.140%   $194.8306   $194.83   $194.85   $194.80  
  Purchase #2 $246.67   6.478%   $262.6493   $262.65   $262.65   $262.60  
  Purchase #3 $40.90   7.623%   $44.0178   $44.02   $44.00   $44.00  
  Purchase #4 $202.69   7.171%   $217.2249   $217.22   $217.20   $217.20  
  Purchase #5 $109.65   5.506%   $115.6873   $115.69   $115.70   $115.70  
  Purchase #6 $46.44   7.791%   $50.0581   $50.06   $50.05   $50.10  
  Purchase #7 $38.74   6.654%   $41.3178   $41.32   $41.30   $41.30  
  7 purchase totals = $868.65       $925.7858   $925.79   $925.75   $925.70