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	$199.75	10.791%	$221.305	$221.31	$221.30	$221.30
Purchase #2	$247.78	5.699%	$261.901	$261.90	$261.90	$261.90
Purchase #3	$64.59	9.800%	$70.9198	$70.92	$70.90	$70.90
Purchase #4	$90.77	4.544%	$94.8946	$94.89	$94.90	$94.90
Purchase #5	$75.95	12.460%	$85.4134	$85.41	$85.40	$85.40
Purchase #6	$101.53	4.643%	$106.244	$106.24	$106.25	$106.20
Purchase #7	$66.56	6.512%	$70.8944	$70.89	$70.90	$70.90
7 purchase totals =	$846.93		$911.5722	$911.56	$911.55	$911.50