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	$233.26	9.349%	$255.0675	$255.07	$255.05	$255.10
Purchase #2	$34.62	7.842%	$37.3349	$37.33	$37.35	$37.30
Purchase #3	$33.49	5.160%	$35.2181	$35.22	$35.20	$35.20
Purchase #4	$195.54	7.223%	$209.6639	$209.66	$209.65	$209.70
Purchase #5	$122.79	3.810%	$127.4683	$127.47	$127.45	$127.50
Purchase #6	$72.38	5.834%	$76.6026	$76.60	$76.60	$76.60
Purchase #7	$192.86	9.866%	$211.8876	$211.89	$211.90	$211.90
7 purchase totals =	$884.94		$953.2429	$953.24	$953.20	$953.30