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	$22.74	13.766%	$25.8704	$25.87	$25.85	$25.90
Purchase #2	$117.40	12.388%	$131.9435	$131.94	$131.95	$131.90
Purchase #3	$86.61	10.733%	$95.9059	$95.91	$95.90	$95.90
Purchase #4	$191.93	12.103%	$215.1593	$215.16	$215.15	$215.20
Purchase #5	$106.57	13.525%	$120.9836	$120.98	$121.00	$121.00
Purchase #6	$83.70	13.387%	$94.9049	$94.90	$94.90	$94.90
Purchase #7	$216.32	12.571%	$243.5136	$243.51	$243.50	$243.50
7 purchase totals =	$825.27		$928.2812	$928.27	$928.25	$928.30