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	$90.95	13.282%	$103.03	$103.03	$103.05	$103.00
Purchase #2	$82.42	11.577%	$91.9618	$91.96	$91.95	$92.00
Purchase #3	$133.25	5.279%	$140.2843	$140.28	$140.30	$140.30
Purchase #4	$146.63	8.695%	$159.3795	$159.38	$159.40	$159.40
Purchase #5	$53.87	12.460%	$60.5822	$60.58	$60.60	$60.60
Purchase #6	$164.60	12.699%	$185.5026	$185.50	$185.50	$185.50
Purchase #7	$209.88	10.134%	$231.1492	$231.15	$231.15	$231.10
7 purchase totals =	$881.60		$971.8896	$971.88	$971.95	$971.90