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	$37.60	7.614%	$40.4629	$40.46	$40.45	$40.50
Purchase #2	$78.83	9.325%	$86.1809	$86.18	$86.20	$86.20
Purchase #3	$68.57	4.238%	$71.476	$71.48	$71.50	$71.50
Purchase #4	$168.79	4.140%	$175.7779	$175.78	$175.80	$175.80
Purchase #5	$49.89	8.710%	$54.2354	$54.24	$54.25	$54.20
Purchase #6	$14.44	9.253%	$15.7761	$15.78	$15.80	$15.80
Purchase #7	$194.89	6.267%	$207.1038	$207.10	$207.10	$207.10
7 purchase totals =	$613.01		$651.0130	$651.02	$651.10	$651.10