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	$117.91	7.844%	$127.1589	$127.16	$127.15	$127.20
Purchase #2	$147.85	8.534%	$160.4675	$160.47	$160.45	$160.50
Purchase #3	$234.52	12.432%	$263.6755	$263.68	$263.70	$263.70
Purchase #4	$124.83	10.441%	$137.8635	$137.86	$137.85	$137.90
Purchase #5	$223.42	4.385%	$233.217	$233.22	$233.20	$233.20
Purchase #6	$162.61	5.573%	$171.6723	$171.67	$171.65	$171.70
Purchase #7	$48.67	6.811%	$51.9849	$51.98	$52.00	$52.00
7 purchase totals =	$1,059.81		$1,146.0396	$1,146.04	$1,146.00	$1,146.20