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	$50.53	5.852%	$53.487	$53.49	$53.50	$53.50
Purchase #2	$87.56	13.344%	$99.244	$99.24	$99.25	$99.20
Purchase #3	$40.26	9.777%	$44.1962	$44.20	$44.20	$44.20
Purchase #4	$234.28	10.391%	$258.624	$258.62	$258.60	$258.60
Purchase #5	$31.81	12.858%	$35.9001	$35.90	$35.90	$35.90
Purchase #6	$55.33	12.412%	$62.1976	$62.20	$62.20	$62.20
Purchase #7	$58.46	12.497%	$65.7657	$65.77	$65.75	$65.80
7 purchase totals =	$558.23		$619.4146	$619.42	$619.40	$619.40