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	$67.61	6.297%	$71.8674	$71.87	$71.85	$71.90
Purchase #2	$48.98	12.631%	$55.1667	$55.17	$55.15	$55.20
Purchase #3	$70.31	12.149%	$78.852	$78.85	$78.85	$78.90
Purchase #4	$155.97	5.787%	$164.996	$165.00	$165.00	$165.00
Purchase #5	$146.66	12.151%	$164.4807	$164.48	$164.50	$164.50
Purchase #6	$166.78	10.673%	$184.5804	$184.58	$184.60	$184.60
Purchase #7	$192.73	13.658%	$219.0531	$219.05	$219.05	$219.10
7 purchase totals =	$849.04		$938.9963	$939.00	$939.00	$939.20