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	$111.30	7.348%	$119.4783	$119.48	$119.50	$119.50
Purchase #2	$158.95	6.142%	$168.7127	$168.71	$168.70	$168.70
Purchase #3	$213.71	9.712%	$234.4655	$234.47	$234.45	$234.50
Purchase #4	$187.33	12.737%	$211.1902	$211.19	$211.20	$211.20
Purchase #5	$121.57	4.863%	$127.4819	$127.48	$127.50	$127.50
Purchase #6	$244.64	7.273%	$262.4327	$262.43	$262.45	$262.40
Purchase #7	$89.28	7.334%	$95.8278	$95.83	$95.85	$95.80
7 purchase totals =	$1,126.78		$1,219.5891	$1,219.59	$1,219.65	$1,219.60