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	$183.57	4.243%	$191.3589	$191.36	$191.35	$191.40
Purchase #2	$72.80	10.347%	$80.3326	$80.33	$80.35	$80.30
Purchase #3	$157.73	3.105%	$162.6275	$162.63	$162.65	$162.60
Purchase #4	$133.97	7.487%	$144.0003	$144.00	$144.00	$144.00
Purchase #5	$136.31	5.758%	$144.1587	$144.16	$144.15	$144.20
Purchase #6	$223.68	4.437%	$233.6047	$233.60	$233.60	$233.60
Purchase #7	$245.65	3.146%	$253.3781	$253.38	$253.40	$253.40
7 purchase totals =	$1,153.71		$1,209.4608	$1,209.46	$1,209.50	$1,209.50