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	$96.49	3.386%	$99.7572	$99.76	$99.75	$99.80
Purchase #2	$147.90	4.556%	$154.6383	$154.64	$154.65	$154.60
Purchase #3	$155.39	6.608%	$165.6582	$165.66	$165.65	$165.70
Purchase #4	$30.77	7.468%	$33.0679	$33.07	$33.05	$33.10
Purchase #5	$63.59	12.448%	$71.5057	$71.51	$71.50	$71.50
Purchase #6	$133.66	7.372%	$143.5134	$143.51	$143.50	$143.50
Purchase #7	$58.29	10.335%	$64.3143	$64.31	$64.30	$64.30
7 purchase totals =	$686.09		$732.4550	$732.46	$732.40	$732.50