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	$233.93	11.373%	$260.5349	$260.53	$260.55	$260.50
Purchase #2	$98.82	5.770%	$104.5219	$104.52	$104.50	$104.50
Purchase #3	$13.56	7.660%	$14.5987	$14.60	$14.60	$14.60
Purchase #4	$50.72	5.696%	$53.609	$53.61	$53.60	$53.60
Purchase #5	$84.78	4.108%	$88.2628	$88.26	$88.25	$88.30
Purchase #6	$168.57	9.422%	$184.4527	$184.45	$184.45	$184.50
Purchase #7	$208.89	4.751%	$218.8144	$218.81	$218.80	$218.80
7 purchase totals =	$859.27		$924.7944	$924.78	$924.75	$924.80