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	$142.60	10.265%	$157.2379	$157.24	$157.25	$157.20
Purchase #2	$122.49	4.384%	$127.86	$127.86	$127.85	$127.90
Purchase #3	$220.90	6.737%	$235.782	$235.78	$235.80	$235.80
Purchase #4	$60.69	11.283%	$67.5377	$67.54	$67.55	$67.50
Purchase #5	$138.74	9.739%	$152.2519	$152.25	$152.25	$152.30
Purchase #6	$49.73	11.705%	$55.5509	$55.55	$55.55	$55.60
Purchase #7	$94.65	11.539%	$105.5717	$105.57	$105.55	$105.60
7 purchase totals =	$829.80		$901.7921	$901.79	$901.80	$901.90