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	$235.95	13.130%	$266.9302	$266.93	$266.95	$266.90
Purchase #2	$126.72	3.559%	$131.23	$131.23	$131.25	$131.20
Purchase #3	$214.88	8.300%	$232.715	$232.72	$232.70	$232.70
Purchase #4	$148.31	7.157%	$158.9245	$158.92	$158.90	$158.90
Purchase #5	$90.55	9.584%	$99.2283	$99.23	$99.25	$99.20
Purchase #6	$98.71	3.199%	$101.8677	$101.87	$101.85	$101.90
Purchase #7	$151.42	10.518%	$167.3464	$167.35	$167.35	$167.30
7 purchase totals =	$1,066.54		$1,158.2421	$1,158.25	$1,158.25	$1,158.10