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	$182.39	7.466%	$196.0072	$196.01	$196.00	$196.00
Purchase #2	$134.61	7.223%	$144.3329	$144.33	$144.35	$144.30
Purchase #3	$83.64	3.272%	$86.3767	$86.38	$86.40	$86.40
Purchase #4	$242.31	11.191%	$269.4269	$269.43	$269.45	$269.40
Purchase #5	$125.68	6.171%	$133.4357	$133.44	$133.45	$133.40
Purchase #6	$55.67	7.662%	$59.9354	$59.94	$59.95	$59.90
Purchase #7	$167.82	13.603%	$190.6486	$190.65	$190.65	$190.60
7 purchase totals =	$992.12		$1,080.1634	$1,080.18	$1,080.25	$1,080.00