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	$116.76	5.618%	$123.3196	$123.32	$123.30	$123.30
Purchase #2	$217.56	9.441%	$238.0998	$238.10	$238.10	$238.10
Purchase #3	$14.60	12.104%	$16.3672	$16.37	$16.35	$16.40
Purchase #4	$29.50	10.173%	$32.501	$32.50	$32.50	$32.50
Purchase #5	$29.83	5.501%	$31.4709	$31.47	$31.45	$31.50
Purchase #6	$198.92	10.847%	$220.4969	$220.50	$220.50	$220.50
Purchase #7	$240.34	8.421%	$260.579	$260.58	$260.60	$260.60
7 purchase totals =	$847.51		$922.8344	$922.84	$922.80	$922.90