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	$57.92	5.382%	$61.0373	$61.04	$61.05	$61.00
Purchase #2	$11.53	9.741%	$12.6531	$12.65	$12.65	$12.70
Purchase #3	$248.57	6.778%	$265.4181	$265.42	$265.40	$265.40
Purchase #4	$249.97	11.801%	$279.469	$279.47	$279.45	$279.50
Purchase #5	$96.67	4.726%	$101.2386	$101.24	$101.25	$101.20
Purchase #6	$240.61	11.203%	$267.5655	$267.57	$267.55	$267.60
Purchase #7	$34.42	9.260%	$37.6073	$37.61	$37.60	$37.60
7 purchase totals =	$939.69		$1,024.9889	$1,025.00	$1,024.95	$1,025.00