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	$229.56	10.243%	$253.0738	$253.07	$253.05	$253.10
Purchase #2	$192.28	12.131%	$215.6055	$215.61	$215.60	$215.60
Purchase #3	$207.70	4.812%	$217.6945	$217.69	$217.70	$217.70
Purchase #4	$76.31	7.848%	$82.2988	$82.30	$82.30	$82.30
Purchase #5	$32.71	8.870%	$35.6114	$35.61	$35.60	$35.60
Purchase #6	$160.72	6.244%	$170.7554	$170.76	$170.75	$170.80
Purchase #7	$186.50	12.868%	$210.4988	$210.50	$210.50	$210.50
7 purchase totals =	$1,085.78		$1,185.5382	$1,185.54	$1,185.50	$1,185.60