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 $86.53   9.233%   $94.5193   $94.52   $94.50   $94.50  
  Purchase #2 $233.98   11.211%   $260.2115   $260.21   $260.20   $260.20  
  Purchase #3 $219.83   8.394%   $238.2825   $238.28   $238.30   $238.30  
  Purchase #4 $153.33   8.348%   $166.13   $166.13   $166.15   $166.10  
  Purchase #5 $165.37   9.663%   $181.3497   $181.35   $181.35   $181.30  
  Purchase #6 $33.70   7.379%   $36.1867   $36.19   $36.20   $36.20  
  Purchase #7 $196.58   11.332%   $218.8564   $218.86   $218.85   $218.90  
  7 purchase totals = $1,089.32       $1,195.5361   $1,195.54   $1,195.55   $1,195.50