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	$144.93	10.733%	$160.4853	$160.49	$160.50	$160.50
Purchase #2	$232.41	7.735%	$250.3869	$250.39	$250.40	$250.40
Purchase #3	$185.74	3.646%	$192.5121	$192.51	$192.50	$192.50
Purchase #4	$131.96	3.222%	$136.2118	$136.21	$136.20	$136.20
Purchase #5	$211.72	5.243%	$222.8205	$222.82	$222.80	$222.80
Purchase #6	$138.93	6.158%	$147.4853	$147.49	$147.50	$147.50
Purchase #7	$99.80	4.751%	$104.5415	$104.54	$104.55	$104.50
7 purchase totals =	$1,145.49		$1,214.4434	$1,214.45	$1,214.45	$1,214.40