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	$75.25	11.255%	$83.7194	$83.72	$83.70	$83.70
Purchase #2	$31.66	12.115%	$35.4956	$35.50	$35.50	$35.50
Purchase #3	$119.93	8.857%	$130.5522	$130.55	$130.55	$130.60
Purchase #4	$237.43	9.674%	$260.399	$260.40	$260.40	$260.40
Purchase #5	$109.75	8.700%	$119.2983	$119.30	$119.30	$119.30
Purchase #6	$230.39	12.219%	$258.5414	$258.54	$258.55	$258.50
Purchase #7	$111.54	4.410%	$116.4589	$116.46	$116.45	$116.50
7 purchase totals =	$915.95		$1,004.4648	$1,004.47	$1,004.45	$1,004.50