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	$71.29	7.717%	$76.7914	$76.79	$76.80	$76.80
Purchase #2	$85.60	13.503%	$97.1586	$97.16	$97.15	$97.20
Purchase #3	$238.39	6.747%	$254.4742	$254.47	$254.45	$254.50
Purchase #4	$35.31	11.554%	$39.3897	$39.39	$39.40	$39.40
Purchase #5	$240.66	10.215%	$265.2434	$265.24	$265.25	$265.20
Purchase #6	$222.32	6.782%	$237.3977	$237.40	$237.40	$237.40
Purchase #7	$86.92	4.295%	$90.6532	$90.65	$90.65	$90.70
7 purchase totals =	$980.49		$1,061.1082	$1,061.10	$1,061.10	$1,061.20