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	$41.53	13.278%	$47.0444	$47.04	$47.05	$47.00
Purchase #2	$81.61	11.349%	$90.8719	$90.87	$90.85	$90.90
Purchase #3	$158.26	10.317%	$174.5877	$174.59	$174.60	$174.60
Purchase #4	$59.60	6.525%	$63.4889	$63.49	$63.50	$63.50
Purchase #5	$249.33	6.388%	$265.2572	$265.26	$265.25	$265.30
Purchase #6	$7.88	7.236%	$8.4502	$8.45	$8.45	$8.50
Purchase #7	$36.53	11.819%	$40.8475	$40.85	$40.85	$40.80
7 purchase totals =	$634.74		$690.5478	$690.55	$690.55	$690.60