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	$38.37	3.853%	$39.8484	$39.85	$39.85	$39.80
Purchase #2	$78.90	5.333%	$83.1077	$83.11	$83.10	$83.10
Purchase #3	$123.30	4.545%	$128.904	$128.90	$128.90	$128.90
Purchase #4	$241.66	3.557%	$250.2558	$250.26	$250.25	$250.30
Purchase #5	$106.32	7.674%	$114.479	$114.48	$114.50	$114.50
Purchase #6	$249.39	5.595%	$263.3434	$263.34	$263.35	$263.30
Purchase #7	$50.78	8.646%	$55.1704	$55.17	$55.15	$55.20
7 purchase totals =	$888.72		$935.1087	$935.11	$935.10	$935.10