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	$83.60	9.262%	$91.343	$91.34	$91.35	$91.30
Purchase #2	$95.45	5.664%	$100.8563	$100.86	$100.85	$100.90
Purchase #3	$38.82	3.835%	$40.3087	$40.31	$40.30	$40.30
Purchase #4	$240.80	13.728%	$273.857	$273.86	$273.85	$273.90
Purchase #5	$64.26	8.447%	$69.688	$69.69	$69.70	$69.70
Purchase #6	$243.35	9.342%	$266.0838	$266.08	$266.10	$266.10
Purchase #7	$17.92	12.215%	$20.1089	$20.11	$20.10	$20.10
7 purchase totals =	$784.20		$862.2457	$862.25	$862.25	$862.30