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	$78.41	10.443%	$86.5984	$86.60	$86.60	$86.60
Purchase #2	$171.43	4.557%	$179.2421	$179.24	$179.25	$179.20
Purchase #3	$38.67	3.830%	$40.1511	$40.15	$40.15	$40.20
Purchase #4	$235.67	6.421%	$250.8024	$250.80	$250.80	$250.80
Purchase #5	$80.39	3.635%	$83.3122	$83.31	$83.30	$83.30
Purchase #6	$76.37	5.359%	$80.4627	$80.46	$80.45	$80.50
Purchase #7	$172.97	5.828%	$183.0507	$183.05	$183.05	$183.10
7 purchase totals =	$853.91		$903.6196	$903.61	$903.60	$903.70