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	$167.81	9.130%	$183.1311	$183.13	$183.15	$183.10
Purchase #2	$206.54	12.680%	$232.7293	$232.73	$232.75	$232.70
Purchase #3	$78.80	8.610%	$85.5847	$85.58	$85.60	$85.60
Purchase #4	$43.48	11.563%	$48.5076	$48.51	$48.50	$48.50
Purchase #5	$30.84	4.410%	$32.2	$32.20	$32.20	$32.20
Purchase #6	$206.63	7.862%	$222.8753	$222.88	$222.90	$222.90
Purchase #7	$185.90	5.633%	$196.3717	$196.37	$196.35	$196.40
7 purchase totals =	$920.00		$1,001.3997	$1,001.40	$1,001.45	$1,001.40