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	$117.77	6.867%	$125.8573	$125.86	$125.85	$125.90
Purchase #2	$122.69	13.742%	$139.5501	$139.55	$139.55	$139.60
Purchase #3	$40.51	3.340%	$41.863	$41.86	$41.85	$41.90
Purchase #4	$89.97	9.399%	$98.4263	$98.43	$98.45	$98.40
Purchase #5	$146.32	13.193%	$165.624	$165.62	$165.60	$165.60
Purchase #6	$46.63	12.426%	$52.4242	$52.42	$52.40	$52.40
Purchase #7	$79.59	7.546%	$85.5959	$85.60	$85.60	$85.60
7 purchase totals =	$643.48		$709.3408	$709.34	$709.30	$709.40