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	$78.26	13.738%	$89.0114	$89.01	$89.00	$89.00
Purchase #2	$41.60	13.600%	$47.2576	$47.26	$47.25	$47.30
Purchase #3	$227.45	8.760%	$247.3746	$247.37	$247.35	$247.40
Purchase #4	$40.28	13.247%	$45.6159	$45.62	$45.60	$45.60
Purchase #5	$44.95	6.533%	$47.8866	$47.89	$47.90	$47.90
Purchase #6	$223.94	3.283%	$231.292	$231.29	$231.30	$231.30
Purchase #7	$118.88	5.649%	$125.5955	$125.60	$125.60	$125.60
7 purchase totals =	$775.36		$834.0336	$834.04	$834.00	$834.10