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 $93.97   8.706%   $102.151   $102.15   $102.15   $102.20  
  Purchase #2 $165.26   13.141%   $186.9768   $186.98   $187.00   $187.00  
  Purchase #3 $129.51   4.236%   $134.996   $135.00   $135.00   $135.00  
  Purchase #4 $181.72   9.396%   $198.7944   $198.79   $198.80   $198.80  
  Purchase #5 $204.82   12.830%   $231.0984   $231.10   $231.10   $231.10  
  Purchase #6 $22.40   10.774%   $24.8134   $24.81   $24.80   $24.80  
  Purchase #7 $151.73   11.442%   $169.0909   $169.09   $169.10   $169.10  
  7 purchase totals = $949.41       $1,047.9209   $1,047.92   $1,047.95   $1,048.00