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	$235.98	11.249%	$262.5254	$262.53	$262.55	$262.50
Purchase #2	$244.66	6.494%	$260.5482	$260.55	$260.55	$260.50
Purchase #3	$100.67	10.545%	$111.2857	$111.29	$111.30	$111.30
Purchase #4	$82.83	13.706%	$94.1827	$94.18	$94.20	$94.20
Purchase #5	$140.76	3.597%	$145.8231	$145.82	$145.80	$145.80
Purchase #6	$211.39	11.112%	$234.8797	$234.88	$234.90	$234.90
Purchase #7	$154.54	10.320%	$170.4885	$170.49	$170.50	$170.50
7 purchase totals =	$1,170.83		$1,279.7333	$1,279.74	$1,279.80	$1,279.70