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	$41.75	7.625%	$44.9334	$44.93	$44.95	$44.90
Purchase #2	$212.67	13.375%	$241.1146	$241.11	$241.10	$241.10
Purchase #3	$146.89	6.385%	$156.2689	$156.27	$156.25	$156.30
Purchase #4	$30.75	4.537%	$32.1451	$32.15	$32.15	$32.10
Purchase #5	$103.98	5.188%	$109.3745	$109.37	$109.35	$109.40
Purchase #6	$228.92	9.687%	$251.0955	$251.10	$251.10	$251.10
Purchase #7	$143.63	11.383%	$159.9794	$159.98	$160.00	$160.00
7 purchase totals =	$908.59		$994.9114	$994.91	$994.90	$994.90