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	$52.52	8.265%	$56.8608	$56.86	$56.85	$56.90
Purchase #2	$66.31	11.339%	$73.8289	$73.83	$73.85	$73.80
Purchase #3	$12.83	6.767%	$13.6982	$13.70	$13.70	$13.70
Purchase #4	$34.67	8.281%	$37.541	$37.54	$37.55	$37.50
Purchase #5	$58.49	11.784%	$65.3825	$65.38	$65.40	$65.40
Purchase #6	$56.85	7.586%	$61.1626	$61.16	$61.15	$61.20
Purchase #7	$216.96	3.367%	$224.265	$224.27	$224.25	$224.30
7 purchase totals =	$498.63		$532.7390	$532.74	$532.75	$532.80