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	$224.60	7.242%	$240.8655	$240.87	$240.85	$240.90
Purchase #2	$189.76	11.153%	$210.9239	$210.92	$210.90	$210.90
Purchase #3	$111.69	6.264%	$118.6863	$118.69	$118.70	$118.70
Purchase #4	$137.25	4.529%	$143.4661	$143.47	$143.45	$143.50
Purchase #5	$93.77	12.683%	$105.6628	$105.66	$105.65	$105.70
Purchase #6	$148.96	5.355%	$156.9368	$156.94	$156.95	$156.90
Purchase #7	$59.25	8.597%	$64.3437	$64.34	$64.35	$64.30
7 purchase totals =	$965.28		$1,040.8851	$1,040.89	$1,040.85	$1,040.90