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	$94.27	5.419%	$99.3785	$99.38	$99.40	$99.40
Purchase #2	$8.89	13.668%	$10.1051	$10.11	$10.10	$10.10
Purchase #3	$57.52	5.361%	$60.6036	$60.60	$60.60	$60.60
Purchase #4	$23.75	5.237%	$24.9938	$24.99	$25.00	$25.00
Purchase #5	$135.86	12.205%	$152.4417	$152.44	$152.45	$152.40
Purchase #6	$64.28	11.737%	$71.8245	$71.82	$71.80	$71.80
Purchase #7	$19.64	7.419%	$21.0971	$21.10	$21.10	$21.10
7 purchase totals =	$404.21		$440.4443	$440.44	$440.45	$440.40