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	$42.46	3.229%	$43.831	$43.83	$43.85	$43.80
Purchase #2	$177.90	6.289%	$189.0881	$189.09	$189.10	$189.10
Purchase #3	$236.64	7.401%	$254.1537	$254.15	$254.15	$254.20
Purchase #4	$221.84	3.616%	$229.8617	$229.86	$229.85	$229.90
Purchase #5	$143.31	3.381%	$148.1553	$148.16	$148.15	$148.20
Purchase #6	$75.98	13.311%	$86.0937	$86.09	$86.10	$86.10
Purchase #7	$102.33	9.381%	$111.9296	$111.93	$111.95	$111.90
7 purchase totals =	$1,000.46		$1,063.1131	$1,063.11	$1,063.15	$1,063.20