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	$197.34	7.587%	$212.3122	$212.31	$212.30	$212.30
Purchase #2	$94.80	11.628%	$105.8233	$105.82	$105.80	$105.80
Purchase #3	$20.65	5.471%	$21.7798	$21.78	$21.80	$21.80
Purchase #4	$42.31	4.363%	$44.156	$44.16	$44.15	$44.20
Purchase #5	$158.83	3.187%	$163.8919	$163.89	$163.90	$163.90
Purchase #6	$151.52	3.253%	$156.4489	$156.45	$156.45	$156.40
Purchase #7	$5.61	9.321%	$6.1329	$6.13	$6.15	$6.10
7 purchase totals =	$671.06		$710.5450	$710.54	$710.55	$710.50