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	$221.70	7.555%	$238.4494	$238.45	$238.45	$238.40
Purchase #2	$157.54	9.542%	$172.5725	$172.57	$172.55	$172.60
Purchase #3	$42.72	11.837%	$47.7768	$47.78	$47.80	$47.80
Purchase #4	$87.62	3.612%	$90.7848	$90.78	$90.80	$90.80
Purchase #5	$35.67	10.255%	$39.328	$39.33	$39.35	$39.30
Purchase #6	$191.89	10.518%	$212.073	$212.07	$212.05	$212.10
Purchase #7	$165.44	10.176%	$182.2752	$182.28	$182.30	$182.30
7 purchase totals =	$902.58		$983.2597	$983.26	$983.30	$983.30