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	$44.85	7.570%	$48.2451	$48.25	$48.25	$48.20
Purchase #2	$188.96	10.504%	$208.8084	$208.81	$208.80	$208.80
Purchase #3	$168.71	10.392%	$186.2423	$186.24	$186.25	$186.20
Purchase #4	$126.84	3.111%	$130.786	$130.79	$130.80	$130.80
Purchase #5	$99.86	5.855%	$105.7068	$105.71	$105.70	$105.70
Purchase #6	$127.69	11.136%	$141.9096	$141.91	$141.90	$141.90
Purchase #7	$102.32	11.230%	$113.8105	$113.81	$113.80	$113.80
7 purchase totals =	$859.23		$935.5087	$935.52	$935.50	$935.40