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	$104.90	4.275%	$109.3845	$109.38	$109.40	$109.40
Purchase #2	$215.50	10.225%	$237.5349	$237.53	$237.55	$237.50
Purchase #3	$249.44	13.384%	$282.825	$282.83	$282.85	$282.80
Purchase #4	$151.46	4.204%	$157.8274	$157.83	$157.85	$157.80
Purchase #5	$129.62	8.565%	$140.722	$140.72	$140.70	$140.70
Purchase #6	$52.61	12.317%	$59.09	$59.09	$59.10	$59.10
Purchase #7	$139.87	12.231%	$156.9775	$156.98	$157.00	$157.00
7 purchase totals =	$1,043.40		$1,144.3613	$1,144.36	$1,144.45	$1,144.30