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	$12.48	7.250%	$13.3848	$13.38	$13.40	$13.40
Purchase #2	$151.48	3.388%	$156.6121	$156.61	$156.60	$156.60
Purchase #3	$219.33	13.814%	$249.6282	$249.63	$249.65	$249.60
Purchase #4	$93.37	6.517%	$99.4549	$99.45	$99.45	$99.50
Purchase #5	$168.57	4.610%	$176.3411	$176.34	$176.35	$176.30
Purchase #6	$120.93	13.273%	$136.981	$136.98	$137.00	$137.00
Purchase #7	$96.42	12.593%	$108.5622	$108.56	$108.55	$108.60
7 purchase totals =	$862.58		$940.9643	$940.95	$941.00	$941.00