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	$20.43	9.396%	$22.3496	$22.35	$22.35	$22.30
Purchase #2	$92.46	7.312%	$99.2207	$99.22	$99.20	$99.20
Purchase #3	$162.46	3.346%	$167.8959	$167.90	$167.90	$167.90
Purchase #4	$158.66	6.698%	$169.287	$169.29	$169.30	$169.30
Purchase #5	$104.37	13.435%	$118.3921	$118.39	$118.40	$118.40
Purchase #6	$42.65	9.375%	$46.6484	$46.65	$46.65	$46.60
Purchase #7	$102.36	13.799%	$116.4847	$116.48	$116.50	$116.50
7 purchase totals =	$683.39		$740.2784	$740.28	$740.30	$740.20