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	$139.56	5.788%	$147.6377	$147.64	$147.65	$147.60
Purchase #2	$96.83	3.332%	$100.0564	$100.06	$100.05	$100.10
Purchase #3	$119.66	10.746%	$132.5187	$132.52	$132.50	$132.50
Purchase #4	$179.52	13.522%	$203.7947	$203.79	$203.80	$203.80
Purchase #5	$209.70	12.560%	$236.0383	$236.04	$236.05	$236.00
Purchase #6	$125.28	11.172%	$139.2763	$139.28	$139.30	$139.30
Purchase #7	$75.37	9.403%	$82.457	$82.46	$82.45	$82.50
7 purchase totals =	$945.92		$1,041.7791	$1,041.79	$1,041.80	$1,041.80