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	$184.66	10.325%	$203.7261	$203.73	$203.75	$203.70
Purchase #2	$185.62	9.778%	$203.7699	$203.77	$203.75	$203.80
Purchase #3	$145.90	6.261%	$155.0348	$155.03	$155.05	$155.00
Purchase #4	$118.96	7.201%	$127.5263	$127.53	$127.55	$127.50
Purchase #5	$141.36	11.752%	$157.9726	$157.97	$157.95	$158.00
Purchase #6	$157.57	11.589%	$175.8308	$175.83	$175.85	$175.80
Purchase #7	$33.54	12.229%	$37.6416	$37.64	$37.65	$37.60
7 purchase totals =	$967.61		$1,061.5021	$1,061.50	$1,061.55	$1,061.40