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	$201.52	9.813%	$221.2952	$221.30	$221.30	$221.30
Purchase #2	$196.67	9.872%	$216.0853	$216.09	$216.10	$216.10
Purchase #3	$50.68	10.695%	$56.1002	$56.10	$56.10	$56.10
Purchase #4	$156.96	8.295%	$169.9798	$169.98	$170.00	$170.00
Purchase #5	$214.37	3.796%	$222.5075	$222.51	$222.50	$222.50
Purchase #6	$101.46	10.197%	$111.8059	$111.81	$111.80	$111.80
Purchase #7	$86.61	10.379%	$95.5993	$95.60	$95.60	$95.60
7 purchase totals =	$1,008.27		$1,093.3732	$1,093.39	$1,093.40	$1,093.40