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	$142.53	7.664%	$153.4535	$153.45	$153.45	$153.50
Purchase #2	$16.27	13.217%	$18.4204	$18.42	$18.40	$18.40
Purchase #3	$156.95	9.842%	$172.397	$172.40	$172.40	$172.40
Purchase #4	$142.88	4.187%	$148.8624	$148.86	$148.85	$148.90
Purchase #5	$69.71	5.279%	$73.39	$73.39	$73.40	$73.40
Purchase #6	$199.31	3.600%	$206.4852	$206.49	$206.50	$206.50
Purchase #7	$137.47	6.365%	$146.22	$146.22	$146.20	$146.20
7 purchase totals =	$865.12		$919.2285	$919.23	$919.20	$919.30