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	$184.71	11.228%	$205.4492	$205.45	$205.45	$205.40
Purchase #2	$147.48	5.497%	$155.587	$155.59	$155.60	$155.60
Purchase #3	$242.30	5.748%	$256.2274	$256.23	$256.25	$256.20
Purchase #4	$216.80	5.555%	$228.8432	$228.84	$228.85	$228.80
Purchase #5	$132.26	4.705%	$138.4828	$138.48	$138.50	$138.50
Purchase #6	$63.46	12.802%	$71.5841	$71.58	$71.60	$71.60
Purchase #7	$120.65	10.109%	$132.8465	$132.85	$132.85	$132.80
7 purchase totals =	$1,107.66		$1,189.0202	$1,189.02	$1,189.10	$1,188.90