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	$80.34	3.250%	$82.9511	$82.95	$82.95	$83.00
Purchase #2	$129.28	12.378%	$145.2823	$145.28	$145.30	$145.30
Purchase #3	$86.80	4.287%	$90.5211	$90.52	$90.50	$90.50
Purchase #4	$81.78	3.249%	$84.437	$84.44	$84.45	$84.40
Purchase #5	$117.86	5.117%	$123.8909	$123.89	$123.90	$123.90
Purchase #6	$48.55	11.331%	$54.0512	$54.05	$54.05	$54.10
Purchase #7	$209.43	4.213%	$218.2533	$218.25	$218.25	$218.30
7 purchase totals =	$754.04		$799.3869	$799.38	$799.40	$799.50