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	$68.80	13.872%	$78.3439	$78.34	$78.35	$78.30
Purchase #2	$200.50	11.188%	$222.9319	$222.93	$222.95	$222.90
Purchase #3	$14.58	13.640%	$16.5687	$16.57	$16.55	$16.60
Purchase #4	$36.57	11.867%	$40.9098	$40.91	$40.90	$40.90
Purchase #5	$169.51	4.661%	$177.4109	$177.41	$177.40	$177.40
Purchase #6	$103.56	7.555%	$111.384	$111.38	$111.40	$111.40
Purchase #7	$213.71	3.443%	$221.068	$221.07	$221.05	$221.10
7 purchase totals =	$807.23		$868.6172	$868.61	$868.60	$868.60