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	$53.78	11.296%	$59.855	$59.86	$59.85	$59.90
Purchase #2	$67.95	6.188%	$72.1547	$72.15	$72.15	$72.20
Purchase #3	$185.68	4.379%	$193.8109	$193.81	$193.80	$193.80
Purchase #4	$53.28	11.712%	$59.5202	$59.52	$59.50	$59.50
Purchase #5	$25.70	4.477%	$26.8506	$26.85	$26.85	$26.90
Purchase #6	$201.31	3.331%	$208.0156	$208.02	$208.00	$208.00
Purchase #7	$227.26	9.324%	$248.4497	$248.45	$248.45	$248.40
7 purchase totals =	$814.96		$868.6567	$868.66	$868.60	$868.70