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	$207.34	13.759%	$235.8679	$235.87	$235.85	$235.90
Purchase #2	$138.92	11.678%	$155.1431	$155.14	$155.15	$155.10
Purchase #3	$228.77	11.669%	$255.4652	$255.47	$255.45	$255.50
Purchase #4	$232.86	11.711%	$260.1302	$260.13	$260.15	$260.10
Purchase #5	$99.97	9.358%	$109.3252	$109.33	$109.35	$109.30
Purchase #6	$36.74	5.679%	$38.8265	$38.83	$38.85	$38.80
Purchase #7	$12.56	10.620%	$13.8939	$13.89	$13.90	$13.90
7 purchase totals =	$957.16		$1,068.6520	$1,068.66	$1,068.70	$1,068.60