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	$81.84	12.567%	$92.1248	$92.12	$92.10	$92.10
Purchase #2	$29.34	8.318%	$31.7805	$31.78	$31.80	$31.80
Purchase #3	$250.82	11.443%	$279.5213	$279.52	$279.50	$279.50
Purchase #4	$10.79	12.459%	$12.1343	$12.13	$12.15	$12.10
Purchase #5	$156.45	3.627%	$162.1244	$162.12	$162.10	$162.10
Purchase #6	$204.40	10.253%	$225.3571	$225.36	$225.35	$225.40
Purchase #7	$248.82	5.255%	$261.8955	$261.90	$261.90	$261.90
7 purchase totals =	$982.46		$1,064.9379	$1,064.93	$1,064.90	$1,064.90