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	$219.63	4.231%	$228.9225	$228.92	$228.90	$228.90
Purchase #2	$93.52	12.114%	$104.849	$104.85	$104.85	$104.80
Purchase #3	$249.60	9.538%	$273.4068	$273.41	$273.40	$273.40
Purchase #4	$141.92	11.549%	$158.3103	$158.31	$158.30	$158.30
Purchase #5	$151.40	12.605%	$170.484	$170.48	$170.50	$170.50
Purchase #6	$40.85	5.595%	$43.1356	$43.14	$43.15	$43.10
Purchase #7	$26.45	12.734%	$29.8181	$29.82	$29.80	$29.80
7 purchase totals =	$923.37		$1,008.9263	$1,008.93	$1,008.90	$1,008.80