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	$196.90	13.520%	$223.5209	$223.52	$223.50	$223.50
Purchase #2	$155.64	7.174%	$166.8056	$166.81	$166.80	$166.80
Purchase #3	$68.66	5.844%	$72.6725	$72.67	$72.65	$72.70
Purchase #4	$65.57	12.112%	$73.5118	$73.51	$73.50	$73.50
Purchase #5	$105.53	13.401%	$119.6721	$119.67	$119.65	$119.70
Purchase #6	$158.88	10.137%	$174.9857	$174.99	$175.00	$175.00
Purchase #7	$196.95	5.796%	$208.3652	$208.37	$208.35	$208.40
7 purchase totals =	$948.13		$1,039.5338	$1,039.54	$1,039.45	$1,039.60