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	$34.47	11.536%	$38.4465	$38.45	$38.45	$38.40
Purchase #2	$241.92	5.611%	$255.4941	$255.49	$255.50	$255.50
Purchase #3	$35.25	11.481%	$39.2971	$39.30	$39.30	$39.30
Purchase #4	$200.35	3.451%	$207.2641	$207.26	$207.25	$207.30
Purchase #5	$95.85	3.800%	$99.4923	$99.49	$99.50	$99.50
Purchase #6	$188.95	11.837%	$211.316	$211.32	$211.30	$211.30
Purchase #7	$23.35	10.840%	$25.8811	$25.88	$25.90	$25.90
7 purchase totals =	$820.14		$877.1912	$877.19	$877.20	$877.20