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	$42.63	6.646%	$45.4632	$45.46	$45.45	$45.50
Purchase #2	$188.82	9.873%	$207.4622	$207.46	$207.45	$207.50
Purchase #3	$60.41	11.556%	$67.391	$67.39	$67.40	$67.40
Purchase #4	$126.80	9.673%	$139.0654	$139.07	$139.05	$139.10
Purchase #5	$138.60	4.333%	$144.6055	$144.61	$144.60	$144.60
Purchase #6	$105.41	5.570%	$111.2813	$111.28	$111.30	$111.30
Purchase #7	$141.49	7.783%	$152.5022	$152.50	$152.50	$152.50
7 purchase totals =	$804.16		$867.7708	$867.77	$867.75	$867.90