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	$152.45	3.550%	$157.862	$157.86	$157.85	$157.90
Purchase #2	$172.54	9.177%	$188.374	$188.37	$188.35	$188.40
Purchase #3	$73.27	6.409%	$77.9659	$77.97	$77.95	$78.00
Purchase #4	$181.29	3.788%	$188.1573	$188.16	$188.15	$188.20
Purchase #5	$20.93	9.605%	$22.9403	$22.94	$22.95	$22.90
Purchase #6	$167.88	13.467%	$190.4884	$190.49	$190.50	$190.50
Purchase #7	$211.68	13.798%	$240.8876	$240.89	$240.90	$240.90
7 purchase totals =	$980.04		$1,066.6755	$1,066.68	$1,066.65	$1,066.80