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	$189.60	12.781%	$213.8328	$213.83	$213.85	$213.80
Purchase #2	$56.60	6.481%	$60.2682	$60.27	$60.25	$60.30
Purchase #3	$104.61	11.335%	$116.4675	$116.47	$116.45	$116.50
Purchase #4	$176.51	8.143%	$190.8832	$190.88	$190.90	$190.90
Purchase #5	$243.87	10.295%	$268.9764	$268.98	$269.00	$269.00
Purchase #6	$143.92	9.242%	$157.2211	$157.22	$157.20	$157.20
Purchase #7	$193.46	11.595%	$215.8917	$215.89	$215.90	$215.90
7 purchase totals =	$1,108.57		$1,223.5409	$1,223.54	$1,223.55	$1,223.60