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 $166.65   9.718%   $182.845   $182.85   $182.85   $182.80  
  Purchase #2 $195.37   6.248%   $207.5767   $207.58   $207.60   $207.60  
  Purchase #3 $113.85   11.132%   $126.5238   $126.52   $126.50   $126.50  
  Purchase #4 $37.28   6.872%   $39.8419   $39.84   $39.85   $39.80  
  Purchase #5 $211.31   10.599%   $233.7067   $233.71   $233.70   $233.70  
  Purchase #6 $244.41   7.426%   $262.5599   $262.56   $262.55   $262.60  
  Purchase #7 $45.31   13.707%   $51.5206   $51.52   $51.50   $51.50  
  7 purchase totals = $1,014.18       $1,104.5746   $1,104.58   $1,104.55   $1,104.50