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	$141.85	7.234%	$152.1114	$152.11	$152.10	$152.10
Purchase #2	$125.36	6.616%	$133.6538	$133.65	$133.65	$133.70
Purchase #3	$124.89	4.716%	$130.7798	$130.78	$130.80	$130.80
Purchase #4	$35.46	5.596%	$37.4443	$37.44	$37.45	$37.40
Purchase #5	$219.75	13.726%	$249.9129	$249.91	$249.90	$249.90
Purchase #6	$74.41	12.203%	$83.4903	$83.49	$83.50	$83.50
Purchase #7	$33.98	11.297%	$37.8187	$37.82	$37.80	$37.80
7 purchase totals =	$755.70		$825.2112	$825.20	$825.20	$825.20