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	$52.26	4.224%	$54.4675	$54.47	$54.45	$54.50
Purchase #2	$203.96	9.229%	$222.7835	$222.78	$222.80	$222.80
Purchase #3	$50.56	11.282%	$56.2642	$56.26	$56.25	$56.30
Purchase #4	$77.29	3.571%	$80.05	$80.05	$80.05	$80.10
Purchase #5	$228.67	11.375%	$254.6812	$254.68	$254.70	$254.70
Purchase #6	$170.74	4.499%	$178.4216	$178.42	$178.40	$178.40
Purchase #7	$119.53	6.733%	$127.578	$127.58	$127.60	$127.60
7 purchase totals =	$903.01		$974.2460	$974.24	$974.25	$974.40