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	$139.81	7.565%	$150.3866	$150.39	$150.40	$150.40
Purchase #2	$46.45	7.156%	$49.774	$49.77	$49.75	$49.80
Purchase #3	$132.57	6.261%	$140.8702	$140.87	$140.85	$140.90
Purchase #4	$80.37	12.567%	$90.4701	$90.47	$90.45	$90.50
Purchase #5	$185.70	10.731%	$205.6275	$205.63	$205.65	$205.60
Purchase #6	$209.42	8.418%	$227.049	$227.05	$227.05	$227.00
Purchase #7	$169.78	12.607%	$191.1842	$191.18	$191.20	$191.20
7 purchase totals =	$964.10		$1,055.3616	$1,055.36	$1,055.35	$1,055.40