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	$189.90	4.223%	$197.9195	$197.92	$197.90	$197.90
Purchase #2	$245.80	12.146%	$275.6549	$275.65	$275.65	$275.70
Purchase #3	$60.62	10.375%	$66.9093	$66.91	$66.90	$66.90
Purchase #4	$29.85	12.219%	$33.4974	$33.50	$33.50	$33.50
Purchase #5	$105.90	12.314%	$118.9405	$118.94	$118.95	$118.90
Purchase #6	$210.65	8.781%	$229.1472	$229.15	$229.15	$229.10
Purchase #7	$193.31	6.404%	$205.6896	$205.69	$205.70	$205.70
7 purchase totals =	$1,036.03		$1,127.7584	$1,127.76	$1,127.75	$1,127.70