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	$88.74	7.136%	$95.0725	$95.07	$95.05	$95.10
Purchase #2	$37.72	7.184%	$40.4298	$40.43	$40.45	$40.40
Purchase #3	$79.93	11.627%	$89.2235	$89.22	$89.20	$89.20
Purchase #4	$18.40	9.499%	$20.1478	$20.15	$20.15	$20.10
Purchase #5	$103.93	3.838%	$107.9188	$107.92	$107.90	$107.90
Purchase #6	$7.76	12.725%	$8.7475	$8.75	$8.75	$8.70
Purchase #7	$160.56	11.874%	$179.6249	$179.62	$179.60	$179.60
7 purchase totals =	$497.04		$541.1648	$541.16	$541.10	$541.00