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	$222.48	13.518%	$252.5548	$252.55	$252.55	$252.60
Purchase #2	$57.31	12.223%	$64.315	$64.32	$64.30	$64.30
Purchase #3	$155.68	13.588%	$176.8338	$176.83	$176.85	$176.80
Purchase #4	$157.62	7.384%	$169.2587	$169.26	$169.25	$169.30
Purchase #5	$186.39	5.235%	$196.1475	$196.15	$196.15	$196.10
Purchase #6	$19.67	10.446%	$21.7247	$21.72	$21.70	$21.70
Purchase #7	$214.90	12.736%	$242.2697	$242.27	$242.25	$242.30
7 purchase totals =	$1,014.05		$1,123.1042	$1,123.10	$1,123.05	$1,123.10