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	$215.83	3.201%	$222.7387	$222.74	$222.75	$222.70
Purchase #2	$78.74	10.734%	$87.192	$87.19	$87.20	$87.20
Purchase #3	$232.86	7.762%	$250.9346	$250.93	$250.95	$250.90
Purchase #4	$24.67	11.274%	$27.4513	$27.45	$27.45	$27.50
Purchase #5	$248.46	6.403%	$264.3689	$264.37	$264.35	$264.40
Purchase #6	$123.96	4.483%	$129.5171	$129.52	$129.50	$129.50
Purchase #7	$105.50	10.314%	$116.3813	$116.38	$116.40	$116.40
7 purchase totals =	$1,030.02		$1,098.5839	$1,098.58	$1,098.60	$1,098.60