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	$129.27	9.537%	$141.5985	$141.60	$141.60	$141.60
Purchase #2	$234.81	4.347%	$245.0172	$245.02	$245.00	$245.00
Purchase #3	$165.62	4.164%	$172.5164	$172.52	$172.50	$172.50
Purchase #4	$10.82	13.681%	$12.3003	$12.30	$12.30	$12.30
Purchase #5	$140.37	11.537%	$156.5645	$156.56	$156.55	$156.60
Purchase #6	$83.51	12.791%	$94.1918	$94.19	$94.20	$94.20
Purchase #7	$248.92	5.224%	$261.9236	$261.92	$261.90	$261.90
7 purchase totals =	$1,013.32		$1,084.1123	$1,084.11	$1,084.05	$1,084.10