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	$237.53	13.525%	$269.6559	$269.66	$269.65	$269.70
Purchase #2	$105.65	11.188%	$117.4701	$117.47	$117.45	$117.50
Purchase #3	$52.29	8.372%	$56.6677	$56.67	$56.65	$56.70
Purchase #4	$147.26	12.294%	$165.3641	$165.36	$165.35	$165.40
Purchase #5	$114.81	7.796%	$123.7606	$123.76	$123.75	$123.80
Purchase #6	$194.27	7.791%	$209.4056	$209.41	$209.40	$209.40
Purchase #7	$91.64	10.145%	$100.9369	$100.94	$100.95	$100.90
7 purchase totals =	$943.45		$1,043.2609	$1,043.27	$1,043.20	$1,043.40