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	$241.57	11.248%	$268.7418	$268.74	$268.75	$268.70
Purchase #2	$30.29	5.434%	$31.936	$31.94	$31.95	$31.90
Purchase #3	$231.59	3.339%	$239.3228	$239.32	$239.30	$239.30
Purchase #4	$84.50	6.374%	$89.886	$89.89	$89.90	$89.90
Purchase #5	$56.43	5.704%	$59.6488	$59.65	$59.65	$59.60
Purchase #6	$41.35	7.117%	$44.2929	$44.29	$44.30	$44.30
Purchase #7	$212.76	8.861%	$231.6127	$231.61	$231.60	$231.60
7 purchase totals =	$898.49		$965.4410	$965.44	$965.45	$965.30