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 $108.38   4.471%   $113.2257   $113.23   $113.25   $113.20  
  Purchase #2 $202.35   5.260%   $212.9936   $212.99   $213.00   $213.00  
  Purchase #3 $128.35   12.453%   $144.3334   $144.33   $144.35   $144.30  
  Purchase #4 $205.52   7.200%   $220.3174   $220.32   $220.30   $220.30  
  Purchase #5 $97.92   7.444%   $105.2092   $105.21   $105.20   $105.20  
  Purchase #6 $124.88   4.405%   $130.381   $130.38   $130.40   $130.40  
  Purchase #7 $164.94   9.295%   $180.2712   $180.27   $180.25   $180.30  
  7 purchase totals = $1,032.34       $1,106.7315   $1,106.73   $1,106.75   $1,106.70