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	$140.55	7.846%	$151.5776	$151.58	$151.60	$151.60
Purchase #2	$165.39	8.420%	$179.3158	$179.32	$179.30	$179.30
Purchase #3	$33.76	4.161%	$35.1648	$35.16	$35.15	$35.20
Purchase #4	$88.52	11.792%	$98.9583	$98.96	$98.95	$99.00
Purchase #5	$85.79	4.147%	$89.3477	$89.35	$89.35	$89.30
Purchase #6	$155.29	13.866%	$176.8225	$176.82	$176.80	$176.80
Purchase #7	$186.86	10.277%	$206.0636	$206.06	$206.05	$206.10
7 purchase totals =	$856.16		$937.2503	$937.25	$937.20	$937.30