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	$67.63	7.622%	$72.7848	$72.78	$72.80	$72.80
Purchase #2	$165.66	4.244%	$172.6906	$172.69	$172.70	$172.70
Purchase #3	$174.67	12.542%	$196.5771	$196.58	$196.60	$196.60
Purchase #4	$24.73	4.114%	$25.7474	$25.75	$25.75	$25.70
Purchase #5	$186.69	6.493%	$198.8118	$198.81	$198.80	$198.80
Purchase #6	$163.56	7.571%	$175.9431	$175.94	$175.95	$175.90
Purchase #7	$241.88	6.671%	$258.0158	$258.02	$258.00	$258.00
7 purchase totals =	$1,024.82		$1,100.5706	$1,100.57	$1,100.60	$1,100.50