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 $32.77   5.346%   $34.5219   $34.52   $34.50   $34.50  
  Purchase #2 $174.48   8.642%   $189.5586   $189.56   $189.55   $189.60  
  Purchase #3 $159.79   5.394%   $168.4091   $168.41   $168.40   $168.40  
  Purchase #4 $167.81   9.421%   $183.6194   $183.62   $183.60   $183.60  
  Purchase #5 $94.99   8.392%   $102.9616   $102.96   $102.95   $103.00  
  Purchase #6 $221.28   3.303%   $228.5889   $228.59   $228.60   $228.60  
  Purchase #7 $114.76   3.869%   $119.2001   $119.20   $119.20   $119.20  
  7 purchase totals = $965.88       $1,026.8596   $1,026.86   $1,026.80   $1,026.90