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	$232.47	11.334%	$258.8181	$258.82	$258.80	$258.80
Purchase #2	$74.31	11.229%	$82.6543	$82.65	$82.65	$82.70
Purchase #3	$14.38	8.769%	$15.641	$15.64	$15.65	$15.60
Purchase #4	$222.38	7.143%	$238.2646	$238.26	$238.25	$238.30
Purchase #5	$50.74	11.718%	$56.6857	$56.69	$56.70	$56.70
Purchase #6	$94.89	6.426%	$100.9876	$100.99	$101.00	$101.00
Purchase #7	$109.59	4.579%	$114.6081	$114.61	$114.60	$114.60
7 purchase totals =	$798.76		$867.6594	$867.66	$867.65	$867.70