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	$200.69	12.570%	$225.9167	$225.92	$225.90	$225.90
Purchase #2	$210.35	12.589%	$236.831	$236.83	$236.85	$236.80
Purchase #3	$208.84	13.667%	$237.3822	$237.38	$237.40	$237.40
Purchase #4	$91.86	9.200%	$100.3111	$100.31	$100.30	$100.30
Purchase #5	$37.93	9.863%	$41.671	$41.67	$41.65	$41.70
Purchase #6	$130.47	11.351%	$145.2796	$145.28	$145.30	$145.30
Purchase #7	$48.47	3.296%	$50.0676	$50.07	$50.05	$50.10
7 purchase totals =	$928.61		$1,037.4592	$1,037.46	$1,037.45	$1,037.50