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	$208.87	4.548%	$218.3694	$218.37	$218.35	$218.40
Purchase #2	$100.84	4.378%	$105.2548	$105.25	$105.25	$105.30
Purchase #3	$84.62	9.544%	$92.6961	$92.70	$92.70	$92.70
Purchase #4	$225.96	10.366%	$249.383	$249.38	$249.40	$249.40
Purchase #5	$80.44	10.513%	$88.8967	$88.90	$88.90	$88.90
Purchase #6	$55.75	6.758%	$59.5176	$59.52	$59.50	$59.50
Purchase #7	$232.90	11.824%	$260.4381	$260.44	$260.45	$260.40
7 purchase totals =	$989.38		$1,074.5557	$1,074.56	$1,074.55	$1,074.60