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	$169.61	12.410%	$190.6586	$190.66	$190.65	$190.70
Purchase #2	$132.95	9.503%	$145.5842	$145.58	$145.60	$145.60
Purchase #3	$188.92	4.232%	$196.9151	$196.92	$196.90	$196.90
Purchase #4	$85.91	9.404%	$93.989	$93.99	$94.00	$94.00
Purchase #5	$78.26	8.828%	$85.1688	$85.17	$85.15	$85.20
Purchase #6	$15.41	12.443%	$17.3275	$17.33	$17.35	$17.30
Purchase #7	$51.37	3.302%	$53.0662	$53.07	$53.05	$53.10
7 purchase totals =	$722.43		$782.7094	$782.72	$782.70	$782.80