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	$104.30	12.721%	$117.568	$117.57	$117.55	$117.60
Purchase #2	$61.82	8.254%	$66.9226	$66.92	$66.90	$66.90
Purchase #3	$32.42	3.841%	$33.6653	$33.67	$33.65	$33.70
Purchase #4	$101.68	7.640%	$109.4484	$109.45	$109.45	$109.40
Purchase #5	$73.89	8.666%	$80.2933	$80.29	$80.30	$80.30
Purchase #6	$88.95	12.786%	$100.3231	$100.32	$100.30	$100.30
Purchase #7	$167.41	11.800%	$187.1644	$187.16	$187.15	$187.20
7 purchase totals =	$630.47		$695.3851	$695.38	$695.30	$695.40