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	$27.25	4.495%	$28.4749	$28.47	$28.45	$28.50
Purchase #2	$99.98	4.422%	$104.4011	$104.40	$104.40	$104.40
Purchase #3	$35.42	5.518%	$37.3745	$37.37	$37.35	$37.40
Purchase #4	$193.34	3.494%	$200.0953	$200.10	$200.10	$200.10
Purchase #5	$205.29	11.609%	$229.1221	$229.12	$229.10	$229.10
Purchase #6	$79.62	7.873%	$85.8885	$85.89	$85.90	$85.90
Purchase #7	$65.67	13.116%	$74.2833	$74.28	$74.30	$74.30
7 purchase totals =	$706.57		$759.6397	$759.63	$759.60	$759.70