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	$88.90	10.526%	$98.2576	$98.26	$98.25	$98.30
Purchase #2	$167.87	9.416%	$183.6766	$183.68	$183.70	$183.70
Purchase #3	$119.91	6.271%	$127.4296	$127.43	$127.45	$127.40
Purchase #4	$196.95	13.667%	$223.8672	$223.87	$223.85	$223.90
Purchase #5	$61.86	6.583%	$65.9322	$65.93	$65.95	$65.90
Purchase #6	$177.87	10.382%	$196.3365	$196.34	$196.35	$196.30
Purchase #7	$225.28	8.443%	$244.3004	$244.30	$244.30	$244.30
7 purchase totals =	$1,038.64		$1,139.8001	$1,139.81	$1,139.85	$1,139.80