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	$30.42	9.354%	$33.2655	$33.27	$33.25	$33.30
Purchase #2	$168.86	3.734%	$175.1652	$175.17	$175.15	$175.20
Purchase #3	$79.50	7.125%	$85.1644	$85.16	$85.15	$85.20
Purchase #4	$51.77	11.276%	$57.6076	$57.61	$57.60	$57.60
Purchase #5	$172.32	4.797%	$180.5862	$180.59	$180.60	$180.60
Purchase #6	$195.34	10.718%	$216.2765	$216.28	$216.30	$216.30
Purchase #7	$109.45	5.611%	$115.5912	$115.59	$115.60	$115.60
7 purchase totals =	$807.66		$863.6566	$863.67	$863.65	$863.80