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	$103.89	4.804%	$108.8809	$108.88	$108.90	$108.90
Purchase #2	$62.38	11.849%	$69.7714	$69.77	$69.75	$69.80
Purchase #3	$194.78	11.343%	$216.8739	$216.87	$216.85	$216.90
Purchase #4	$123.37	4.276%	$128.6453	$128.65	$128.65	$128.60
Purchase #5	$98.32	9.539%	$107.6987	$107.70	$107.70	$107.70
Purchase #6	$203.85	6.755%	$217.6201	$217.62	$217.60	$217.60
Purchase #7	$180.82	8.679%	$196.5134	$196.51	$196.50	$196.50
7 purchase totals =	$967.41		$1,046.0037	$1,046.00	$1,045.95	$1,046.00