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	$65.97	11.716%	$73.699	$73.70	$73.70	$73.70
Purchase #2	$131.87	12.153%	$147.8962	$147.90	$147.90	$147.90
Purchase #3	$160.82	13.464%	$182.4728	$182.47	$182.45	$182.50
Purchase #4	$59.28	4.797%	$62.1237	$62.12	$62.10	$62.10
Purchase #5	$87.29	3.322%	$90.1898	$90.19	$90.20	$90.20
Purchase #6	$65.36	12.111%	$73.2757	$73.28	$73.30	$73.30
Purchase #7	$93.56	6.218%	$99.3776	$99.38	$99.40	$99.40
7 purchase totals =	$664.15		$729.0348	$729.04	$729.05	$729.10