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	$121.69	4.832%	$127.5701	$127.57	$127.55	$127.60
Purchase #2	$182.40	4.761%	$191.0841	$191.08	$191.10	$191.10
Purchase #3	$39.96	13.564%	$45.3802	$45.38	$45.40	$45.40
Purchase #4	$92.72	9.510%	$101.5377	$101.54	$101.55	$101.50
Purchase #5	$196.42	5.544%	$207.3095	$207.31	$207.30	$207.30
Purchase #6	$5.78	3.442%	$5.9789	$5.98	$6.00	$6.00
Purchase #7	$36.34	5.627%	$38.3849	$38.38	$38.40	$38.40
7 purchase totals =	$675.31		$717.2454	$717.24	$717.30	$717.30