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	$135.45	13.633%	$153.9159	$153.92	$153.90	$153.90
Purchase #2	$59.81	7.428%	$64.2527	$64.25	$64.25	$64.30
Purchase #3	$35.90	12.776%	$40.4866	$40.49	$40.50	$40.50
Purchase #4	$118.46	7.468%	$127.3066	$127.31	$127.30	$127.30
Purchase #5	$26.66	9.715%	$29.25	$29.25	$29.25	$29.30
Purchase #6	$66.96	12.572%	$75.3782	$75.38	$75.40	$75.40
Purchase #7	$205.62	13.229%	$232.8215	$232.82	$232.80	$232.80
7 purchase totals =	$648.86		$723.4115	$723.42	$723.40	$723.50