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	$49.49	3.680%	$51.3112	$51.31	$51.30	$51.30
Purchase #2	$197.52	12.702%	$222.609	$222.61	$222.60	$222.60
Purchase #3	$11.92	3.684%	$12.3591	$12.36	$12.35	$12.40
Purchase #4	$69.71	12.432%	$78.3763	$78.38	$78.40	$78.40
Purchase #5	$92.45	4.706%	$96.8007	$96.80	$96.80	$96.80
Purchase #6	$204.52	9.284%	$223.5076	$223.51	$223.50	$223.50
Purchase #7	$72.78	3.467%	$75.3033	$75.30	$75.30	$75.30
7 purchase totals =	$698.39		$760.2672	$760.27	$760.25	$760.30