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	$164.85	12.582%	$185.5914	$185.59	$185.60	$185.60
Purchase #2	$68.72	12.827%	$77.5347	$77.53	$77.55	$77.50
Purchase #3	$62.47	13.867%	$71.1327	$71.13	$71.15	$71.10
Purchase #4	$227.25	6.342%	$241.6622	$241.66	$241.65	$241.70
Purchase #5	$227.39	12.460%	$255.7228	$255.72	$255.70	$255.70
Purchase #6	$42.39	8.222%	$45.8753	$45.88	$45.90	$45.90
Purchase #7	$96.39	9.836%	$105.8709	$105.87	$105.85	$105.90
7 purchase totals =	$889.46		$983.3900	$983.38	$983.40	$983.40