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	$36.31	5.411%	$38.2747	$38.27	$38.25	$38.30
Purchase #2	$112.81	13.509%	$128.0495	$128.05	$128.05	$128.00
Purchase #3	$89.28	12.525%	$100.4623	$100.46	$100.45	$100.50
Purchase #4	$97.50	7.219%	$104.5385	$104.54	$104.55	$104.50
Purchase #5	$238.87	8.167%	$258.3785	$258.38	$258.40	$258.40
Purchase #6	$221.73	11.496%	$247.2201	$247.22	$247.20	$247.20
Purchase #7	$141.43	9.781%	$155.2633	$155.26	$155.25	$155.30
7 purchase totals =	$937.93		$1,032.1869	$1,032.18	$1,032.15	$1,032.20