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	$190.52	4.809%	$199.6821	$199.68	$199.70	$199.70
Purchase #2	$141.73	11.782%	$158.4286	$158.43	$158.45	$158.40
Purchase #3	$82.45	9.587%	$90.3545	$90.35	$90.35	$90.40
Purchase #4	$66.98	11.196%	$74.4791	$74.48	$74.50	$74.50
Purchase #5	$143.52	4.654%	$150.1994	$150.20	$150.20	$150.20
Purchase #6	$114.85	9.371%	$125.6126	$125.61	$125.60	$125.60
Purchase #7	$195.88	13.802%	$222.9154	$222.92	$222.90	$222.90
7 purchase totals =	$935.93		$1,021.6717	$1,021.67	$1,021.70	$1,021.70