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	$57.31	6.837%	$61.2283	$61.23	$61.25	$61.20
Purchase #2	$48.53	8.207%	$52.5129	$52.51	$52.50	$52.50
Purchase #3	$159.42	7.629%	$171.5822	$171.58	$171.60	$171.60
Purchase #4	$209.45	6.287%	$222.6181	$222.62	$222.60	$222.60
Purchase #5	$202.89	3.163%	$209.3074	$209.31	$209.30	$209.30
Purchase #6	$104.58	12.676%	$117.8366	$117.84	$117.85	$117.80
Purchase #7	$198.29	11.250%	$220.5976	$220.60	$220.60	$220.60
7 purchase totals =	$980.47		$1,055.6831	$1,055.69	$1,055.70	$1,055.60