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	$49.74	3.471%	$51.4665	$51.47	$51.45	$51.50
Purchase #2	$166.34	3.378%	$171.959	$171.96	$171.95	$172.00
Purchase #3	$32.30	12.620%	$36.3763	$36.38	$36.40	$36.40
Purchase #4	$143.72	9.549%	$157.4438	$157.44	$157.45	$157.40
Purchase #5	$235.72	11.730%	$263.37	$263.37	$263.35	$263.40
Purchase #6	$38.59	4.441%	$40.3038	$40.30	$40.30	$40.30
Purchase #7	$248.83	10.628%	$275.2757	$275.28	$275.30	$275.30
7 purchase totals =	$915.24		$996.1951	$996.20	$996.20	$996.30