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	$224.68	11.209%	$249.8644	$249.86	$249.85	$249.90
Purchase #2	$212.43	5.262%	$223.6081	$223.61	$223.60	$223.60
Purchase #3	$40.69	5.190%	$42.8018	$42.80	$42.80	$42.80
Purchase #4	$95.30	4.200%	$99.3026	$99.30	$99.30	$99.30
Purchase #5	$134.71	3.303%	$139.1595	$139.16	$139.15	$139.20
Purchase #6	$81.34	4.785%	$85.2321	$85.23	$85.25	$85.20
Purchase #7	$206.60	9.798%	$226.8427	$226.84	$226.85	$226.80
7 purchase totals =	$995.75		$1,066.8112	$1,066.80	$1,066.80	$1,066.80