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	$57.72	11.177%	$64.1714	$64.17	$64.15	$64.20
Purchase #2	$122.47	11.849%	$136.9815	$136.98	$137.00	$137.00
Purchase #3	$118.38	4.762%	$124.0173	$124.02	$124.00	$124.00
Purchase #4	$102.89	9.204%	$112.36	$112.36	$112.35	$112.40
Purchase #5	$37.98	11.244%	$42.2505	$42.25	$42.25	$42.30
Purchase #6	$131.58	12.148%	$147.5643	$147.56	$147.55	$147.60
Purchase #7	$50.87	7.314%	$54.5906	$54.59	$54.60	$54.60
7 purchase totals =	$621.89		$681.9356	$681.93	$681.90	$682.10