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 $174.68   12.167%   $195.9333   $195.93   $195.95   $195.90  
  Purchase #2 $118.92   7.155%   $127.4287   $127.43   $127.45   $127.40  
  Purchase #3 $17.29   4.592%   $18.084   $18.08   $18.10   $18.10  
  Purchase #4 $243.48   9.809%   $267.363   $267.36   $267.35   $267.40  
  Purchase #5 $167.74   8.652%   $182.2529   $182.25   $182.25   $182.30  
  Purchase #6 $40.33   4.107%   $41.9864   $41.99   $42.00   $42.00  
  Purchase #7 $206.83   6.198%   $219.6493   $219.65   $219.65   $219.60  
  7 purchase totals = $969.27       $1,052.6976   $1,052.69   $1,052.75   $1,052.70