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	$31.71	12.846%	$35.7835	$35.78	$35.80	$35.80
Purchase #2	$78.50	4.637%	$82.14	$82.14	$82.15	$82.10
Purchase #3	$233.92	11.249%	$260.2337	$260.23	$260.25	$260.20
Purchase #4	$113.77	10.868%	$126.1345	$126.13	$126.15	$126.10
Purchase #5	$215.78	4.298%	$225.0542	$225.05	$225.05	$225.10
Purchase #6	$194.96	8.579%	$211.6856	$211.69	$211.70	$211.70
Purchase #7	$111.86	7.794%	$120.5784	$120.58	$120.60	$120.60
7 purchase totals =	$980.50		$1,061.6099	$1,061.60	$1,061.70	$1,061.60