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	$216.26	10.413%	$238.7792	$238.78	$238.80	$238.80
Purchase #2	$100.40	11.281%	$111.7261	$111.73	$111.75	$111.70
Purchase #3	$6.72	7.830%	$7.2462	$7.25	$7.25	$7.20
Purchase #4	$20.60	6.237%	$21.8848	$21.88	$21.90	$21.90
Purchase #5	$157.78	6.545%	$168.1067	$168.11	$168.10	$168.10
Purchase #6	$245.29	6.199%	$260.4955	$260.50	$260.50	$260.50
Purchase #7	$247.64	6.272%	$263.172	$263.17	$263.15	$263.20
7 purchase totals =	$994.69		$1,071.4105	$1,071.42	$1,071.45	$1,071.40