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	$106.83	3.173%	$110.2197	$110.22	$110.20	$110.20
Purchase #2	$250.34	13.609%	$284.4088	$284.41	$284.40	$284.40
Purchase #3	$53.29	13.458%	$60.4618	$60.46	$60.45	$60.50
Purchase #4	$99.37	7.561%	$106.8834	$106.88	$106.90	$106.90
Purchase #5	$189.91	11.178%	$211.1381	$211.14	$211.15	$211.10
Purchase #6	$121.64	4.653%	$127.2999	$127.30	$127.30	$127.30
Purchase #7	$136.32	11.110%	$151.4652	$151.47	$151.45	$151.50
7 purchase totals =	$957.70		$1,051.8769	$1,051.88	$1,051.85	$1,051.90