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 $248.70   5.761%   $263.0276   $263.03   $263.05   $263.00  
  Purchase #2 $39.58   5.351%   $41.6979   $41.70   $41.70   $41.70  
  Purchase #3 $175.79   3.404%   $181.7739   $181.77   $181.75   $181.80  
  Purchase #4 $64.65   3.810%   $67.1132   $67.11   $67.10   $67.10  
  Purchase #5 $211.75   9.584%   $232.0441   $232.04   $232.05   $232.00  
  Purchase #6 $107.53   7.799%   $115.9163   $115.92   $115.90   $115.90  
  Purchase #7 $150.36   7.507%   $161.6475   $161.65   $161.65   $161.60  
  7 purchase totals = $998.36       $1,063.2205   $1,063.22   $1,063.20   $1,063.10