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	$150.27	9.445%	$164.463	$164.46	$164.45	$164.50
Purchase #2	$195.29	13.295%	$221.2538	$221.25	$221.25	$221.30
Purchase #3	$214.69	12.868%	$242.3163	$242.32	$242.30	$242.30
Purchase #4	$55.99	6.682%	$59.7313	$59.73	$59.75	$59.70
Purchase #5	$180.90	13.263%	$204.8928	$204.89	$204.90	$204.90
Purchase #6	$204.74	12.294%	$229.9107	$229.91	$229.90	$229.90
Purchase #7	$80.55	10.733%	$89.1954	$89.20	$89.20	$89.20
7 purchase totals =	$1,082.43		$1,211.7633	$1,211.76	$1,211.75	$1,211.80