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	$158.81	7.147%	$170.1602	$170.16	$170.15	$170.20
Purchase #2	$246.59	8.221%	$266.8622	$266.86	$266.85	$266.90
Purchase #3	$114.49	11.203%	$127.3163	$127.32	$127.30	$127.30
Purchase #4	$147.67	4.306%	$154.0287	$154.03	$154.05	$154.00
Purchase #5	$85.48	4.285%	$89.1428	$89.14	$89.15	$89.10
Purchase #6	$151.50	8.683%	$164.6547	$164.65	$164.65	$164.70
Purchase #7	$62.32	5.831%	$65.9539	$65.95	$65.95	$66.00
7 purchase totals =	$966.86		$1,038.1188	$1,038.11	$1,038.10	$1,038.20