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	$33.68	7.620%	$36.2464	$36.25	$36.25	$36.20
Purchase #2	$78.81	9.546%	$86.3332	$86.33	$86.35	$86.30
Purchase #3	$140.45	7.291%	$150.6902	$150.69	$150.70	$150.70
Purchase #4	$238.26	5.134%	$250.4923	$250.49	$250.50	$250.50
Purchase #5	$137.77	9.199%	$150.4435	$150.44	$150.45	$150.40
Purchase #6	$149.82	5.670%	$158.3148	$158.31	$158.30	$158.30
Purchase #7	$155.48	11.296%	$173.043	$173.04	$173.05	$173.00
7 purchase totals =	$934.27		$1,005.5634	$1,005.55	$1,005.60	$1,005.40