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	$168.66	7.680%	$181.6131	$181.61	$181.60	$181.60
Purchase #2	$247.29	10.243%	$272.6199	$272.62	$272.60	$272.60
Purchase #3	$78.88	13.594%	$89.6029	$89.60	$89.60	$89.60
Purchase #4	$50.63	13.585%	$57.5081	$57.51	$57.50	$57.50
Purchase #5	$101.85	7.665%	$109.6568	$109.66	$109.65	$109.70
Purchase #6	$91.30	9.347%	$99.8338	$99.83	$99.85	$99.80
Purchase #7	$56.54	13.735%	$64.3058	$64.31	$64.30	$64.30
7 purchase totals =	$795.15		$875.1404	$875.14	$875.10	$875.10