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 $201.35   4.615%   $210.6423   $210.64   $210.65   $210.60  
  Purchase #2 $177.88   11.726%   $198.7382   $198.74   $198.75   $198.70  
  Purchase #3 $52.56   7.415%   $56.4573   $56.46   $56.45   $56.50  
  Purchase #4 $52.93   13.514%   $60.083   $60.08   $60.10   $60.10  
  Purchase #5 $212.66   8.532%   $230.8042   $230.80   $230.80   $230.80  
  Purchase #6 $182.66   4.231%   $190.3883   $190.39   $190.40   $190.40  
  Purchase #7 $179.62   13.639%   $204.1184   $204.12   $204.10   $204.10  
  7 purchase totals = $1,059.66       $1,151.2317   $1,151.23   $1,151.25   $1,151.20