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	$23.58	5.867%	$24.9634	$24.96	$24.95	$25.00
Purchase #2	$238.84	4.468%	$249.5114	$249.51	$249.50	$249.50
Purchase #3	$152.65	6.434%	$162.4715	$162.47	$162.45	$162.50
Purchase #4	$149.37	13.481%	$169.5066	$169.51	$169.50	$169.50
Purchase #5	$241.42	4.219%	$251.6055	$251.61	$251.60	$251.60
Purchase #6	$233.60	13.275%	$264.6104	$264.61	$264.60	$264.60
Purchase #7	$26.86	5.750%	$28.4045	$28.40	$28.40	$28.40
7 purchase totals =	$1,066.32		$1,151.0733	$1,151.07	$1,151.00	$1,151.10