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	$65.67	10.612%	$72.6389	$72.64	$72.65	$72.60
Purchase #2	$242.55	6.566%	$258.4758	$258.48	$258.50	$258.50
Purchase #3	$192.51	12.261%	$216.1137	$216.11	$216.10	$216.10
Purchase #4	$78.60	9.151%	$85.7927	$85.79	$85.80	$85.80
Purchase #5	$123.39	11.620%	$137.7279	$137.73	$137.75	$137.70
Purchase #6	$90.91	8.675%	$98.7964	$98.80	$98.80	$98.80
Purchase #7	$221.29	4.694%	$231.6774	$231.68	$231.70	$231.70
7 purchase totals =	$1,014.92		$1,101.2228	$1,101.23	$1,101.30	$1,101.20