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 $87.66   8.753%   $95.3329   $95.33   $95.35   $95.30  
  Purchase #2 $104.57   4.732%   $109.5183   $109.52   $109.50   $109.50  
  Purchase #3 $37.44   4.305%   $39.0518   $39.05   $39.05   $39.10  
  Purchase #4 $184.40   8.332%   $199.7642   $199.76   $199.75   $199.80  
  Purchase #5 $199.37   6.544%   $212.4168   $212.42   $212.40   $212.40  
  Purchase #6 $210.54   6.227%   $223.6503   $223.65   $223.65   $223.70  
  Purchase #7 $244.71   6.391%   $260.3494   $260.35   $260.35   $260.30  
  7 purchase totals = $1,068.69       $1,140.0837   $1,140.08   $1,140.05   $1,140.10