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	$119.25	6.601%	$127.1217	$127.12	$127.10	$127.10
Purchase #2	$180.32	13.551%	$204.7552	$204.76	$204.75	$204.80
Purchase #3	$62.78	12.678%	$70.7392	$70.74	$70.75	$70.70
Purchase #4	$128.81	11.626%	$143.7855	$143.79	$143.80	$143.80
Purchase #5	$100.34	11.569%	$111.9483	$111.95	$111.95	$111.90
Purchase #6	$85.82	6.399%	$91.3116	$91.31	$91.30	$91.30
Purchase #7	$174.61	13.302%	$197.8366	$197.84	$197.85	$197.80
7 purchase totals =	$851.93		$947.4981	$947.51	$947.50	$947.40