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	$141.87	7.741%	$152.8522	$152.85	$152.85	$152.90
Purchase #2	$210.53	13.679%	$239.3284	$239.33	$239.35	$239.30
Purchase #3	$55.85	10.347%	$61.6288	$61.63	$61.65	$61.60
Purchase #4	$239.33	3.379%	$247.417	$247.42	$247.40	$247.40
Purchase #5	$145.77	12.567%	$164.0889	$164.09	$164.10	$164.10
Purchase #6	$242.39	12.422%	$272.4997	$272.50	$272.50	$272.50
Purchase #7	$25.52	7.870%	$27.5284	$27.53	$27.55	$27.50
7 purchase totals =	$1,061.26		$1,165.3434	$1,165.35	$1,165.40	$1,165.30