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	$106.78	5.274%	$112.4116	$112.41	$112.40	$112.40
Purchase #2	$28.96	12.825%	$32.6741	$32.67	$32.65	$32.70
Purchase #3	$66.33	6.769%	$70.8199	$70.82	$70.80	$70.80
Purchase #4	$236.64	9.652%	$259.4805	$259.48	$259.50	$259.50
Purchase #5	$144.51	13.517%	$164.0434	$164.04	$164.05	$164.00
Purchase #6	$231.77	10.550%	$256.2217	$256.22	$256.20	$256.20
Purchase #7	$9.77	9.445%	$10.6928	$10.69	$10.70	$10.70
7 purchase totals =	$824.76		$906.3440	$906.33	$906.30	$906.30