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	$101.49	3.865%	$105.4126	$105.41	$105.40	$105.40
Purchase #2	$14.37	7.810%	$15.4923	$15.49	$15.50	$15.50
Purchase #3	$98.29	8.156%	$106.3065	$106.31	$106.30	$106.30
Purchase #4	$176.25	5.205%	$185.4238	$185.42	$185.40	$185.40
Purchase #5	$148.44	12.779%	$167.4091	$167.41	$167.40	$167.40
Purchase #6	$216.67	10.256%	$238.8917	$238.89	$238.90	$238.90
Purchase #7	$172.53	8.775%	$187.6695	$187.67	$187.65	$187.70
7 purchase totals =	$928.04		$1,006.6055	$1,006.60	$1,006.55	$1,006.60