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	$85.34	5.232%	$89.805	$89.81	$89.80	$89.80
Purchase #2	$66.61	3.761%	$69.1152	$69.12	$69.10	$69.10
Purchase #3	$219.56	12.774%	$247.6066	$247.61	$247.60	$247.60
Purchase #4	$89.43	11.456%	$99.6751	$99.68	$99.70	$99.70
Purchase #5	$204.26	4.229%	$212.8982	$212.90	$212.90	$212.90
Purchase #6	$144.89	13.858%	$164.9689	$164.97	$164.95	$165.00
Purchase #7	$225.56	3.356%	$233.1298	$233.13	$233.15	$233.10
7 purchase totals =	$1,035.65		$1,117.1988	$1,117.22	$1,117.20	$1,117.20