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	$199.91	7.345%	$214.5934	$214.59	$214.60	$214.60
Purchase #2	$163.89	4.640%	$171.4945	$171.49	$171.50	$171.50
Purchase #3	$200.43	13.545%	$227.5782	$227.58	$227.60	$227.60
Purchase #4	$137.76	4.400%	$143.8214	$143.82	$143.80	$143.80
Purchase #5	$107.73	3.618%	$111.6277	$111.63	$111.65	$111.60
Purchase #6	$245.60	3.512%	$254.2255	$254.23	$254.25	$254.20
Purchase #7	$165.76	12.579%	$186.611	$186.61	$186.60	$186.60
7 purchase totals =	$1,221.08		$1,309.9517	$1,309.95	$1,310.00	$1,309.90