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 $61.74   4.765%   $64.6819   $64.68   $64.70   $64.70  
  Purchase #2 $167.86   6.757%   $179.2023   $179.20   $179.20   $179.20  
  Purchase #3 $234.77   12.678%   $264.5341   $264.53   $264.55   $264.50  
  Purchase #4 $75.35   5.700%   $79.645   $79.65   $79.65   $79.60  
  Purchase #5 $60.76   7.323%   $65.2095   $65.21   $65.20   $65.20  
  Purchase #6 $213.76   6.173%   $226.9554   $226.96   $226.95   $227.00  
  Purchase #7 $212.61   4.357%   $221.8734   $221.87   $221.85   $221.90  
  7 purchase totals = $1,026.85       $1,102.1016   $1,102.10   $1,102.10   $1,102.10