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	$172.79	12.461%	$194.3214	$194.32	$194.30	$194.30
Purchase #2	$196.31	7.216%	$210.4757	$210.48	$210.50	$210.50
Purchase #3	$93.93	3.506%	$97.2232	$97.22	$97.20	$97.20
Purchase #4	$60.67	7.205%	$65.0413	$65.04	$65.05	$65.00
Purchase #5	$62.90	5.502%	$66.3608	$66.36	$66.35	$66.40
Purchase #6	$169.48	11.795%	$189.4702	$189.47	$189.45	$189.50
Purchase #7	$230.45	5.644%	$243.4566	$243.46	$243.45	$243.50
7 purchase totals =	$986.53		$1,066.3492	$1,066.35	$1,066.30	$1,066.40