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 $54.52   5.826%   $57.6963   $57.70   $57.70   $57.70  
  Purchase #2 $91.66   6.810%   $97.902   $97.90   $97.90   $97.90  
  Purchase #3 $64.52   5.376%   $67.9886   $67.99   $68.00   $68.00  
  Purchase #4 $180.70   11.759%   $201.9485   $201.95   $201.95   $201.90  
  Purchase #5 $167.26   9.194%   $182.6379   $182.64   $182.65   $182.60  
  Purchase #6 $220.93   5.368%   $232.7895   $232.79   $232.80   $232.80  
  Purchase #7 $196.97   7.684%   $212.1052   $212.11   $212.10   $212.10  
  7 purchase totals = $976.56       $1,053.0680   $1,053.08   $1,053.10   $1,053.00