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	$197.34	12.237%	$221.4885	$221.49	$221.50	$221.50
Purchase #2	$144.66	3.324%	$149.4685	$149.47	$149.45	$149.50
Purchase #3	$51.89	10.430%	$57.3021	$57.30	$57.30	$57.30
Purchase #4	$45.35	6.872%	$48.4665	$48.47	$48.45	$48.50
Purchase #5	$35.69	5.849%	$37.7775	$37.78	$37.80	$37.80
Purchase #6	$161.38	6.657%	$172.1231	$172.12	$172.10	$172.10
Purchase #7	$101.83	4.157%	$106.0631	$106.06	$106.05	$106.10
7 purchase totals =	$738.14		$792.6893	$792.69	$792.65	$792.80