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	$146.51	5.468%	$154.5212	$154.52	$154.50	$154.50
Purchase #2	$17.27	8.675%	$18.7682	$18.77	$18.75	$18.80
Purchase #3	$249.70	9.473%	$273.3541	$273.35	$273.35	$273.40
Purchase #4	$35.69	5.106%	$37.5123	$37.51	$37.50	$37.50
Purchase #5	$229.33	10.829%	$254.1641	$254.16	$254.15	$254.20
Purchase #6	$13.46	5.206%	$14.1607	$14.16	$14.15	$14.20
Purchase #7	$118.63	9.814%	$130.2723	$130.27	$130.25	$130.30
7 purchase totals =	$810.59		$882.7529	$882.74	$882.65	$882.90