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	$37.33	10.567%	$41.2747	$41.27	$41.25	$41.30
Purchase #2	$41.74	7.868%	$45.0241	$45.02	$45.00	$45.00
Purchase #3	$228.78	5.252%	$240.7955	$240.80	$240.80	$240.80
Purchase #4	$230.87	5.721%	$244.0781	$244.08	$244.10	$244.10
Purchase #5	$202.58	11.213%	$225.2953	$225.30	$225.30	$225.30
Purchase #6	$153.97	11.449%	$171.598	$171.60	$171.60	$171.60
Purchase #7	$126.67	11.635%	$141.4081	$141.41	$141.40	$141.40
7 purchase totals =	$1,021.94		$1,109.4738	$1,109.48	$1,109.45	$1,109.50