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	$148.31	7.143%	$158.9038	$158.90	$158.90	$158.90
Purchase #2	$80.78	7.813%	$87.0913	$87.09	$87.10	$87.10
Purchase #3	$91.96	6.854%	$98.2629	$98.26	$98.25	$98.30
Purchase #4	$139.69	8.460%	$151.5078	$151.51	$151.50	$151.50
Purchase #5	$138.43	10.515%	$152.9859	$152.99	$153.00	$153.00
Purchase #6	$175.41	7.369%	$188.336	$188.34	$188.35	$188.30
Purchase #7	$132.93	6.533%	$141.6143	$141.61	$141.60	$141.60
7 purchase totals =	$907.51		$978.7020	$978.70	$978.70	$978.70