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	$164.89	12.647%	$185.7436	$185.74	$185.75	$185.70
Purchase #2	$145.63	4.422%	$152.0698	$152.07	$152.05	$152.10
Purchase #3	$99.70	13.152%	$112.8125	$112.81	$112.80	$112.80
Purchase #4	$97.78	5.871%	$103.5207	$103.52	$103.50	$103.50
Purchase #5	$210.30	8.715%	$228.6276	$228.63	$228.65	$228.60
Purchase #6	$80.87	8.872%	$88.0448	$88.04	$88.05	$88.00
Purchase #7	$32.25	10.559%	$35.6553	$35.66	$35.65	$35.70
7 purchase totals =	$831.42		$906.4743	$906.47	$906.45	$906.40