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	$54.38	10.204%	$59.9289	$59.93	$59.95	$59.90
Purchase #2	$204.68	12.175%	$229.5998	$229.60	$229.60	$229.60
Purchase #3	$45.61	10.526%	$50.4109	$50.41	$50.40	$50.40
Purchase #4	$236.41	12.745%	$266.5405	$266.54	$266.55	$266.50
Purchase #5	$130.81	13.789%	$148.8474	$148.85	$148.85	$148.80
Purchase #6	$6.93	9.458%	$7.5854	$7.59	$7.60	$7.60
Purchase #7	$56.54	11.699%	$63.1546	$63.15	$63.15	$63.20
7 purchase totals =	$735.36		$826.0675	$826.07	$826.10	$826.00