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	$66.45	4.813%	$69.6482	$69.65	$69.65	$69.60
Purchase #2	$158.86	7.802%	$171.2543	$171.25	$171.25	$171.30
Purchase #3	$193.37	9.513%	$211.7653	$211.77	$211.75	$211.80
Purchase #4	$98.44	8.289%	$106.5997	$106.60	$106.60	$106.60
Purchase #5	$199.42	8.381%	$216.1334	$216.13	$216.15	$216.10
Purchase #6	$136.41	5.165%	$143.4556	$143.46	$143.45	$143.50
Purchase #7	$135.43	12.673%	$152.593	$152.59	$152.60	$152.60
7 purchase totals =	$988.38		$1,071.4495	$1,071.45	$1,071.45	$1,071.50