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	$164.80	10.873%	$182.7187	$182.72	$182.70	$182.70
Purchase #2	$245.88	10.454%	$271.5843	$271.58	$271.60	$271.60
Purchase #3	$75.32	10.433%	$83.1781	$83.18	$83.20	$83.20
Purchase #4	$38.59	9.273%	$42.1685	$42.17	$42.15	$42.20
Purchase #5	$29.89	8.855%	$32.5368	$32.54	$32.55	$32.50
Purchase #6	$23.62	9.254%	$25.8058	$25.81	$25.80	$25.80
Purchase #7	$132.75	8.861%	$144.513	$144.51	$144.50	$144.50
7 purchase totals =	$710.85		$782.5052	$782.51	$782.50	$782.50