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	$129.57	8.723%	$140.8724	$140.87	$140.85	$140.90
Purchase #2	$167.59	7.631%	$180.3788	$180.38	$180.40	$180.40
Purchase #3	$32.43	6.519%	$34.5441	$34.54	$34.55	$34.50
Purchase #4	$36.74	10.263%	$40.5106	$40.51	$40.50	$40.50
Purchase #5	$5.96	9.750%	$6.5411	$6.54	$6.55	$6.50
Purchase #6	$55.56	13.187%	$62.8867	$62.89	$62.90	$62.90
Purchase #7	$38.88	5.333%	$40.9535	$40.95	$40.95	$41.00
7 purchase totals =	$466.73		$506.6872	$506.68	$506.70	$506.70