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	$68.81	11.133%	$76.4706	$76.47	$76.45	$76.50
Purchase #2	$73.82	4.830%	$77.3855	$77.39	$77.40	$77.40
Purchase #3	$210.58	13.232%	$238.4439	$238.44	$238.45	$238.40
Purchase #4	$140.54	3.259%	$145.1202	$145.12	$145.10	$145.10
Purchase #5	$223.32	5.302%	$235.1604	$235.16	$235.15	$235.20
Purchase #6	$16.56	9.291%	$18.0986	$18.10	$18.10	$18.10
Purchase #7	$175.77	11.610%	$196.1769	$196.18	$196.20	$196.20
7 purchase totals =	$909.40		$986.8561	$986.86	$986.85	$986.90