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	$53.68	10.527%	$59.3309	$59.33	$59.35	$59.30
Purchase #2	$201.74	7.131%	$216.1261	$216.13	$216.15	$216.10
Purchase #3	$152.43	6.624%	$162.527	$162.53	$162.55	$162.50
Purchase #4	$221.45	9.755%	$243.0524	$243.05	$243.05	$243.10
Purchase #5	$176.81	4.653%	$185.037	$185.04	$185.05	$185.00
Purchase #6	$172.51	6.494%	$183.7128	$183.71	$183.70	$183.70
Purchase #7	$207.28	11.818%	$231.7764	$231.78	$231.80	$231.80
7 purchase totals =	$1,185.90		$1,281.5626	$1,281.57	$1,281.65	$1,281.50