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	$197.80	10.850%	$219.2613	$219.26	$219.25	$219.30
Purchase #2	$78.80	13.149%	$89.1614	$89.16	$89.15	$89.20
Purchase #3	$34.76	13.667%	$39.5106	$39.51	$39.50	$39.50
Purchase #4	$149.39	12.229%	$167.6589	$167.66	$167.65	$167.70
Purchase #5	$207.89	6.187%	$220.7522	$220.75	$220.75	$220.80
Purchase #6	$62.63	8.294%	$67.8245	$67.82	$67.80	$67.80
Purchase #7	$28.80	12.161%	$32.3024	$32.30	$32.30	$32.30
7 purchase totals =	$760.07		$836.4713	$836.46	$836.40	$836.60