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	$32.75	7.863%	$35.3251	$35.33	$35.35	$35.30
Purchase #2	$143.96	9.778%	$158.0364	$158.04	$158.05	$158.00
Purchase #3	$246.40	11.448%	$274.6079	$274.61	$274.60	$274.60
Purchase #4	$177.48	4.530%	$185.5198	$185.52	$185.50	$185.50
Purchase #5	$130.71	13.599%	$148.4853	$148.49	$148.50	$148.50
Purchase #6	$228.82	5.779%	$242.0435	$242.04	$242.05	$242.00
Purchase #7	$174.96	12.295%	$196.4713	$196.47	$196.45	$196.50
7 purchase totals =	$1,135.08		$1,240.4893	$1,240.50	$1,240.50	$1,240.40