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	$172.75	13.838%	$196.6551	$196.66	$196.65	$196.70
Purchase #2	$79.77	8.239%	$86.3423	$86.34	$86.35	$86.30
Purchase #3	$86.72	10.431%	$95.7658	$95.77	$95.75	$95.80
Purchase #4	$85.34	4.591%	$89.258	$89.26	$89.25	$89.30
Purchase #5	$86.36	13.152%	$97.7181	$97.72	$97.70	$97.70
Purchase #6	$227.58	9.175%	$248.4605	$248.46	$248.45	$248.50
Purchase #7	$112.91	4.704%	$118.2213	$118.22	$118.20	$118.20
7 purchase totals =	$851.43		$932.4211	$932.43	$932.35	$932.50