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	$224.71	10.135%	$247.4844	$247.48	$247.50	$247.50
Purchase #2	$197.25	11.207%	$219.3558	$219.36	$219.35	$219.40
Purchase #3	$175.49	11.767%	$196.1399	$196.14	$196.15	$196.10
Purchase #4	$139.43	11.205%	$155.0531	$155.05	$155.05	$155.10
Purchase #5	$199.37	8.394%	$216.1051	$216.11	$216.10	$216.10
Purchase #6	$227.70	5.355%	$239.8933	$239.89	$239.90	$239.90
Purchase #7	$56.63	5.705%	$59.8607	$59.86	$59.85	$59.90
7 purchase totals =	$1,220.58		$1,333.8923	$1,333.89	$1,333.90	$1,334.00