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	$175.28	5.265%	$184.5085	$184.51	$184.50	$184.50
Purchase #2	$93.41	8.484%	$101.3349	$101.33	$101.35	$101.30
Purchase #3	$99.44	9.213%	$108.6014	$108.60	$108.60	$108.60
Purchase #4	$232.86	11.258%	$259.0754	$259.08	$259.10	$259.10
Purchase #5	$152.80	3.614%	$158.3222	$158.32	$158.30	$158.30
Purchase #6	$91.44	8.680%	$99.377	$99.38	$99.40	$99.40
Purchase #7	$235.84	10.369%	$260.2942	$260.29	$260.30	$260.30
7 purchase totals =	$1,081.07		$1,171.5136	$1,171.51	$1,171.55	$1,171.50