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	$33.60	12.249%	$37.7157	$37.72	$37.70	$37.70
Purchase #2	$75.36	10.618%	$83.3617	$83.36	$83.35	$83.40
Purchase #3	$43.46	5.354%	$45.7868	$45.79	$45.80	$45.80
Purchase #4	$70.86	11.458%	$78.9791	$78.98	$79.00	$79.00
Purchase #5	$123.30	3.711%	$127.8757	$127.88	$127.90	$127.90
Purchase #6	$15.56	9.692%	$17.0681	$17.07	$17.05	$17.10
Purchase #7	$45.47	9.206%	$49.656	$49.66	$49.65	$49.70
7 purchase totals =	$407.61		$440.4431	$440.46	$440.45	$440.60