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	$221.67	8.341%	$240.1595	$240.16	$240.15	$240.20
Purchase #2	$76.65	6.354%	$81.5203	$81.52	$81.50	$81.50
Purchase #3	$228.52	13.280%	$258.8675	$258.87	$258.85	$258.90
Purchase #4	$113.90	4.609%	$119.1497	$119.15	$119.15	$119.10
Purchase #5	$127.39	4.477%	$133.0933	$133.09	$133.10	$133.10
Purchase #6	$143.73	7.468%	$154.4638	$154.46	$154.45	$154.50
Purchase #7	$80.57	10.560%	$89.0782	$89.08	$89.10	$89.10
7 purchase totals =	$992.43		$1,076.3323	$1,076.33	$1,076.30	$1,076.40