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	$185.93	7.603%	$200.0663	$200.07	$200.05	$200.10
Purchase #2	$47.78	11.389%	$53.2217	$53.22	$53.20	$53.20
Purchase #3	$14.95	6.308%	$15.893	$15.89	$15.90	$15.90
Purchase #4	$126.39	4.208%	$131.7085	$131.71	$131.70	$131.70
Purchase #5	$180.76	7.810%	$194.8774	$194.88	$194.90	$194.90
Purchase #6	$106.68	3.259%	$110.1567	$110.16	$110.15	$110.20
Purchase #7	$105.34	5.424%	$111.0536	$111.05	$111.05	$111.10
7 purchase totals =	$767.83		$816.9772	$816.98	$816.95	$817.10