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	$152.99	12.656%	$172.3524	$172.35	$172.35	$172.40
Purchase #2	$224.60	10.294%	$247.7203	$247.72	$247.70	$247.70
Purchase #3	$113.67	10.714%	$125.8486	$125.85	$125.85	$125.80
Purchase #4	$143.44	5.384%	$151.1628	$151.16	$151.15	$151.20
Purchase #5	$85.70	4.488%	$89.5462	$89.55	$89.55	$89.50
Purchase #6	$186.41	12.807%	$210.2835	$210.28	$210.30	$210.30
Purchase #7	$81.49	8.441%	$88.3686	$88.37	$88.35	$88.40
7 purchase totals =	$988.30		$1,085.2824	$1,085.28	$1,085.25	$1,085.30