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 $194.62   7.392%   $209.0063   $209.01   $209.00   $209.00  
  Purchase #2 $211.72   3.279%   $218.6623   $218.66   $218.65   $218.70  
  Purchase #3 $159.93   7.445%   $171.8368   $171.84   $171.85   $171.80  
  Purchase #4 $235.91   7.809%   $254.3322   $254.33   $254.35   $254.30  
  Purchase #5 $53.93   11.173%   $59.9556   $59.96   $59.95   $60.00  
  Purchase #6 $112.55   12.755%   $126.9058   $126.91   $126.90   $126.90  
  Purchase #7 $51.72   6.523%   $55.0937   $55.09   $55.10   $55.10  
  7 purchase totals = $1,020.38       $1,095.7927   $1,095.80   $1,095.80   $1,095.80