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	$209.73	4.413%	$218.9854	$218.99	$219.00	$219.00
Purchase #2	$40.71	4.411%	$42.5057	$42.51	$42.50	$42.50
Purchase #3	$197.57	11.795%	$220.8734	$220.87	$220.85	$220.90
Purchase #4	$29.61	9.225%	$32.3415	$32.34	$32.35	$32.30
Purchase #5	$149.84	10.513%	$165.5927	$165.59	$165.60	$165.60
Purchase #6	$170.34	12.719%	$192.0055	$192.01	$192.00	$192.00
Purchase #7	$34.52	8.574%	$37.4797	$37.48	$37.50	$37.50
7 purchase totals =	$832.32		$909.7839	$909.79	$909.80	$909.80