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	$143.46	13.718%	$163.1398	$163.14	$163.15	$163.10
Purchase #2	$39.71	9.754%	$43.5833	$43.58	$43.60	$43.60
Purchase #3	$189.35	5.180%	$199.1583	$199.16	$199.15	$199.20
Purchase #4	$175.51	13.456%	$199.1266	$199.13	$199.15	$199.10
Purchase #5	$131.49	7.656%	$141.5569	$141.56	$141.55	$141.60
Purchase #6	$154.83	11.410%	$172.4961	$172.50	$172.50	$172.50
Purchase #7	$178.93	7.173%	$191.7646	$191.76	$191.75	$191.80
7 purchase totals =	$1,013.28		$1,110.8256	$1,110.83	$1,110.85	$1,110.90