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	$99.58	12.224%	$111.7527	$111.75	$111.75	$111.80
Purchase #2	$206.67	4.756%	$216.4992	$216.50	$216.50	$216.50
Purchase #3	$248.47	10.806%	$275.3197	$275.32	$275.30	$275.30
Purchase #4	$190.79	3.321%	$197.1261	$197.13	$197.15	$197.10
Purchase #5	$189.34	11.122%	$210.3984	$210.40	$210.40	$210.40
Purchase #6	$173.95	6.686%	$185.5803	$185.58	$185.60	$185.60
Purchase #7	$178.32	9.696%	$195.6099	$195.61	$195.60	$195.60
7 purchase totals =	$1,287.12		$1,392.2863	$1,392.29	$1,392.30	$1,392.30