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	$201.70	13.495%	$228.9194	$228.92	$228.90	$228.90
Purchase #2	$102.30	8.621%	$111.1193	$111.12	$111.10	$111.10
Purchase #3	$44.63	4.854%	$46.7963	$46.80	$46.80	$46.80
Purchase #4	$66.32	6.303%	$70.5001	$70.50	$70.50	$70.50
Purchase #5	$34.43	3.155%	$35.5163	$35.52	$35.50	$35.50
Purchase #6	$154.53	9.781%	$169.6446	$169.64	$169.65	$169.60
Purchase #7	$63.81	13.659%	$72.5258	$72.53	$72.55	$72.50
7 purchase totals =	$667.72		$735.0218	$735.03	$735.00	$734.90