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	$175.55	12.660%	$197.7746	$197.77	$197.75	$197.80
Purchase #2	$142.31	11.622%	$158.8493	$158.85	$158.85	$158.80
Purchase #3	$131.72	11.806%	$147.2709	$147.27	$147.25	$147.30
Purchase #4	$147.83	5.530%	$156.005	$156.01	$156.00	$156.00
Purchase #5	$160.76	4.448%	$167.9106	$167.91	$167.90	$167.90
Purchase #6	$154.40	11.560%	$172.2486	$172.25	$172.25	$172.20
Purchase #7	$28.98	13.693%	$32.9482	$32.95	$32.95	$32.90
7 purchase totals =	$941.55		$1,033.0072	$1,033.01	$1,032.95	$1,032.90