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	$54.72	10.171%	$60.2856	$60.29	$60.30	$60.30
Purchase #2	$18.32	11.338%	$20.3971	$20.40	$20.40	$20.40
Purchase #3	$20.52	4.469%	$21.437	$21.44	$21.45	$21.40
Purchase #4	$70.63	11.585%	$78.8125	$78.81	$78.80	$78.80
Purchase #5	$83.68	13.663%	$95.1132	$95.11	$95.10	$95.10
Purchase #6	$42.66	6.874%	$45.5924	$45.59	$45.60	$45.60
Purchase #7	$123.63	13.276%	$140.0431	$140.04	$140.05	$140.00
7 purchase totals =	$414.16		$461.6809	$461.68	$461.70	$461.60