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	$64.79	3.438%	$67.0175	$67.02	$67.00	$67.00
Purchase #2	$33.43	9.200%	$36.5056	$36.51	$36.50	$36.50
Purchase #3	$196.35	10.454%	$216.8764	$216.88	$216.90	$216.90
Purchase #4	$83.81	3.317%	$86.59	$86.59	$86.60	$86.60
Purchase #5	$155.49	12.690%	$175.2217	$175.22	$175.20	$175.20
Purchase #6	$133.84	6.500%	$142.5396	$142.54	$142.55	$142.50
Purchase #7	$194.85	12.346%	$218.9062	$218.91	$218.90	$218.90
7 purchase totals =	$862.56		$943.6570	$943.67	$943.65	$943.60