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	$149.28	7.446%	$160.3954	$160.40	$160.40	$160.40
Purchase #2	$233.94	10.843%	$259.3061	$259.31	$259.30	$259.30
Purchase #3	$37.80	7.186%	$40.5163	$40.52	$40.50	$40.50
Purchase #4	$247.54	13.132%	$280.047	$280.05	$280.05	$280.00
Purchase #5	$107.68	11.288%	$119.8349	$119.83	$119.85	$119.80
Purchase #6	$35.94	10.691%	$39.7823	$39.78	$39.80	$39.80
Purchase #7	$151.38	11.231%	$168.3815	$168.38	$168.40	$168.40
7 purchase totals =	$963.56		$1,068.2635	$1,068.27	$1,068.30	$1,068.20