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	$60.75	8.443%	$65.8791	$65.88	$65.90	$65.90
Purchase #2	$144.53	4.111%	$150.4716	$150.47	$150.45	$150.50
Purchase #3	$159.74	10.236%	$176.091	$176.09	$176.10	$176.10
Purchase #4	$85.83	13.460%	$97.3827	$97.38	$97.40	$97.40
Purchase #5	$111.66	6.689%	$119.1289	$119.13	$119.15	$119.10
Purchase #6	$76.65	9.179%	$83.6857	$83.69	$83.70	$83.70
Purchase #7	$94.53	12.295%	$106.1525	$106.15	$106.15	$106.20
7 purchase totals =	$733.69		$798.7915	$798.79	$798.85	$798.90