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	$141.68	10.738%	$156.8936	$156.89	$156.90	$156.90
Purchase #2	$44.54	4.712%	$46.6387	$46.64	$46.65	$46.60
Purchase #3	$67.64	12.699%	$76.2296	$76.23	$76.25	$76.20
Purchase #4	$164.42	6.611%	$175.2898	$175.29	$175.30	$175.30
Purchase #5	$68.72	5.502%	$72.501	$72.50	$72.50	$72.50
Purchase #6	$12.67	8.265%	$13.7172	$13.72	$13.70	$13.70
Purchase #7	$181.90	9.512%	$199.2023	$199.20	$199.20	$199.20
7 purchase totals =	$681.57		$740.4722	$740.47	$740.50	$740.40