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	$47.85	10.429%	$52.8403	$52.84	$52.85	$52.80
Purchase #2	$96.49	4.534%	$100.8649	$100.86	$100.85	$100.90
Purchase #3	$33.67	8.563%	$36.5532	$36.55	$36.55	$36.60
Purchase #4	$143.76	9.161%	$156.9299	$156.93	$156.95	$156.90
Purchase #5	$102.51	3.148%	$105.737	$105.74	$105.75	$105.70
Purchase #6	$34.76	11.771%	$38.8516	$38.85	$38.85	$38.90
Purchase #7	$34.89	4.682%	$36.5235	$36.52	$36.50	$36.50
7 purchase totals =	$493.93		$528.3004	$528.29	$528.30	$528.30