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	$48.26	4.823%	$50.5876	$50.59	$50.60	$50.60
Purchase #2	$54.50	6.700%	$58.1515	$58.15	$58.15	$58.20
Purchase #3	$41.89	9.225%	$45.7544	$45.75	$45.75	$45.80
Purchase #4	$73.39	6.414%	$78.0972	$78.10	$78.10	$78.10
Purchase #5	$151.60	3.735%	$157.2623	$157.26	$157.25	$157.30
Purchase #6	$27.54	12.284%	$30.923	$30.92	$30.90	$30.90
Purchase #7	$70.98	7.296%	$76.1587	$76.16	$76.15	$76.20
7 purchase totals =	$468.16		$496.9347	$496.93	$496.90	$497.10