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	$165.32	3.551%	$171.1905	$171.19	$171.20	$171.20
Purchase #2	$10.71	5.198%	$11.2667	$11.27	$11.25	$11.30
Purchase #3	$244.83	13.459%	$277.7817	$277.78	$277.80	$277.80
Purchase #4	$126.71	13.435%	$143.7335	$143.73	$143.75	$143.70
Purchase #5	$89.71	12.228%	$100.6797	$100.68	$100.70	$100.70
Purchase #6	$64.78	13.221%	$73.3446	$73.34	$73.35	$73.30
Purchase #7	$140.88	7.507%	$151.4559	$151.46	$151.45	$151.50
7 purchase totals =	$842.94		$929.4526	$929.45	$929.50	$929.50