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	$188.54	11.439%	$210.1071	$210.11	$210.10	$210.10
Purchase #2	$191.30	13.364%	$216.8653	$216.87	$216.85	$216.90
Purchase #3	$229.98	12.590%	$258.9345	$258.93	$258.95	$258.90
Purchase #4	$100.78	10.138%	$110.9971	$111.00	$111.00	$111.00
Purchase #5	$222.85	8.315%	$241.38	$241.38	$241.40	$241.40
Purchase #6	$13.59	13.152%	$15.3774	$15.38	$15.40	$15.40
Purchase #7	$45.77	3.856%	$47.5349	$47.53	$47.55	$47.50
7 purchase totals =	$992.81		$1,101.1963	$1,101.20	$1,101.25	$1,101.20