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 $67.61   9.438%   $73.991   $73.99   $74.00   $74.00  
  Purchase #2 $218.35   7.631%   $235.0123   $235.01   $235.00   $235.00  
  Purchase #3 $150.57   10.172%   $165.886   $165.89   $165.90   $165.90  
  Purchase #4 $44.30   6.327%   $47.1029   $47.10   $47.10   $47.10  
  Purchase #5 $164.92   10.333%   $181.9612   $181.96   $181.95   $182.00  
  Purchase #6 $195.29   12.630%   $219.9551   $219.96   $219.95   $220.00  
  Purchase #7 $152.96   11.527%   $170.5917   $170.59   $170.60   $170.60  
  7 purchase totals = $994.00       $1,094.5002   $1,094.50   $1,094.50   $1,094.60