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	$155.88	12.837%	$175.8903	$175.89	$175.90	$175.90
Purchase #2	$88.53	13.423%	$100.4134	$100.41	$100.40	$100.40
Purchase #3	$163.65	3.119%	$168.7542	$168.75	$168.75	$168.80
Purchase #4	$241.30	8.536%	$261.8974	$261.90	$261.90	$261.90
Purchase #5	$127.54	11.737%	$142.5094	$142.51	$142.50	$142.50
Purchase #6	$12.33	11.294%	$13.7226	$13.72	$13.70	$13.70
Purchase #7	$159.83	7.471%	$171.7709	$171.77	$171.75	$171.80
7 purchase totals =	$949.06		$1,034.9582	$1,034.95	$1,034.90	$1,035.00