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	$218.39	9.554%	$239.255	$239.26	$239.25	$239.30
Purchase #2	$77.85	5.503%	$82.1341	$82.13	$82.15	$82.10
Purchase #3	$59.37	8.329%	$64.3149	$64.31	$64.30	$64.30
Purchase #4	$147.30	7.589%	$158.4786	$158.48	$158.50	$158.50
Purchase #5	$38.31	4.829%	$40.16	$40.16	$40.15	$40.20
Purchase #6	$167.64	7.842%	$180.7863	$180.79	$180.80	$180.80
Purchase #7	$201.47	5.872%	$213.3003	$213.30	$213.30	$213.30
7 purchase totals =	$910.33		$978.4292	$978.43	$978.45	$978.50