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	$59.34	13.849%	$67.558	$67.56	$67.55	$67.60
Purchase #2	$239.34	4.787%	$250.7972	$250.80	$250.80	$250.80
Purchase #3	$56.72	4.338%	$59.1805	$59.18	$59.20	$59.20
Purchase #4	$51.44	10.687%	$56.9374	$56.94	$56.95	$56.90
Purchase #5	$86.52	7.366%	$92.8931	$92.89	$92.90	$92.90
Purchase #6	$147.47	7.736%	$158.8783	$158.88	$158.90	$158.90
Purchase #7	$39.84	12.131%	$44.673	$44.67	$44.65	$44.70
7 purchase totals =	$680.67		$730.9175	$730.92	$730.95	$731.00