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	$126.83	8.597%	$137.7336	$137.73	$137.75	$137.70
Purchase #2	$112.95	13.764%	$128.4964	$128.50	$128.50	$128.50
Purchase #3	$217.87	5.397%	$229.6284	$229.63	$229.65	$229.60
Purchase #4	$128.38	11.238%	$142.8073	$142.81	$142.80	$142.80
Purchase #5	$155.33	6.380%	$165.2401	$165.24	$165.25	$165.20
Purchase #6	$176.49	11.281%	$196.3998	$196.40	$196.40	$196.40
Purchase #7	$233.67	5.794%	$247.2088	$247.21	$247.20	$247.20
7 purchase totals =	$1,151.52		$1,247.5144	$1,247.52	$1,247.55	$1,247.40