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	$10.35	7.404%	$11.1163	$11.12	$11.10	$11.10
Purchase #2	$111.80	5.393%	$117.8294	$117.83	$117.85	$117.80
Purchase #3	$65.85	5.255%	$69.3104	$69.31	$69.30	$69.30
Purchase #4	$210.31	4.198%	$219.1388	$219.14	$219.15	$219.10
Purchase #5	$52.60	7.216%	$56.3956	$56.40	$56.40	$56.40
Purchase #6	$61.69	9.655%	$67.6462	$67.65	$67.65	$67.60
Purchase #7	$198.79	11.752%	$222.1518	$222.15	$222.15	$222.20
7 purchase totals =	$711.39		$763.5885	$763.60	$763.60	$763.50