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	$148.85	11.398%	$165.8159	$165.82	$165.80	$165.80
Purchase #2	$162.41	11.566%	$181.1943	$181.19	$181.20	$181.20
Purchase #3	$122.73	4.602%	$128.378	$128.38	$128.40	$128.40
Purchase #4	$11.78	9.650%	$12.9168	$12.92	$12.90	$12.90
Purchase #5	$236.67	11.260%	$263.319	$263.32	$263.30	$263.30
Purchase #6	$38.59	11.540%	$43.0433	$43.04	$43.05	$43.00
Purchase #7	$85.32	11.258%	$94.9253	$94.93	$94.95	$94.90
7 purchase totals =	$806.35		$889.5926	$889.60	$889.60	$889.50