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	$43.84	6.185%	$46.5515	$46.55	$46.55	$46.60
Purchase #2	$39.59	12.715%	$44.6239	$44.62	$44.60	$44.60
Purchase #3	$38.35	4.553%	$40.0961	$40.10	$40.10	$40.10
Purchase #4	$66.95	4.201%	$69.7626	$69.76	$69.75	$69.80
Purchase #5	$56.95	4.531%	$59.5304	$59.53	$59.55	$59.50
Purchase #6	$74.96	4.383%	$78.2455	$78.25	$78.25	$78.20
Purchase #7	$50.90	7.794%	$54.8671	$54.87	$54.85	$54.90
7 purchase totals =	$371.54		$393.6771	$393.68	$393.65	$393.70