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	$82.31	13.675%	$93.5659	$93.57	$93.55	$93.60
Purchase #2	$224.79	7.330%	$241.2671	$241.27	$241.25	$241.30
Purchase #3	$226.95	4.447%	$237.0425	$237.04	$237.05	$237.00
Purchase #4	$135.28	13.428%	$153.4454	$153.45	$153.45	$153.40
Purchase #5	$222.29	6.626%	$237.0189	$237.02	$237.00	$237.00
Purchase #6	$79.92	13.358%	$90.5957	$90.60	$90.60	$90.60
Purchase #7	$137.45	4.767%	$144.0022	$144.00	$144.00	$144.00
7 purchase totals =	$1,108.99		$1,196.9377	$1,196.95	$1,196.90	$1,196.90