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	$142.58	7.209%	$152.8586	$152.86	$152.85	$152.90
Purchase #2	$184.56	6.560%	$196.6671	$196.67	$196.65	$196.70
Purchase #3	$35.48	9.599%	$38.8857	$38.89	$38.90	$38.90
Purchase #4	$228.94	10.282%	$252.4796	$252.48	$252.50	$252.50
Purchase #5	$111.70	12.601%	$125.7753	$125.78	$125.80	$125.80
Purchase #6	$227.93	12.393%	$256.1774	$256.18	$256.20	$256.20
Purchase #7	$85.56	7.815%	$92.2465	$92.25	$92.25	$92.20
7 purchase totals =	$1,016.75		$1,115.0902	$1,115.11	$1,115.15	$1,115.20