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 $161.50   8.537%   $175.2873   $175.29   $175.30   $175.30  
  Purchase #2 $31.64   10.506%   $34.9641   $34.96   $34.95   $35.00  
  Purchase #3 $42.77   6.568%   $45.5791   $45.58   $45.60   $45.60  
  Purchase #4 $52.66   5.442%   $55.5258   $55.53   $55.55   $55.50  
  Purchase #5 $236.60   11.710%   $264.3059   $264.31   $264.30   $264.30  
  Purchase #6 $178.64   12.526%   $201.0164   $201.02   $201.00   $201.00  
  Purchase #7 $165.91   3.268%   $171.3319   $171.33   $171.35   $171.30  
  7 purchase totals = $869.72       $948.0105   $948.02   $948.05   $948.00