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	$34.50	3.222%	$35.6116	$35.61	$35.60	$35.60
Purchase #2	$156.69	10.145%	$172.5862	$172.59	$172.60	$172.60
Purchase #3	$93.78	12.629%	$105.6235	$105.62	$105.60	$105.60
Purchase #4	$227.78	8.811%	$247.8497	$247.85	$247.85	$247.80
Purchase #5	$73.61	9.255%	$80.4226	$80.42	$80.40	$80.40
Purchase #6	$180.30	4.580%	$188.5577	$188.56	$188.55	$188.60
Purchase #7	$43.77	10.776%	$48.4867	$48.49	$48.50	$48.50
7 purchase totals =	$810.43		$879.1380	$879.14	$879.10	$879.10