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	$168.43	3.452%	$174.2442	$174.24	$174.25	$174.20
Purchase #2	$112.49	10.184%	$123.946	$123.95	$123.95	$123.90
Purchase #3	$160.67	7.424%	$172.5981	$172.60	$172.60	$172.60
Purchase #4	$247.25	11.159%	$274.8406	$274.84	$274.85	$274.80
Purchase #5	$168.25	4.550%	$175.9054	$175.91	$175.90	$175.90
Purchase #6	$103.31	10.218%	$113.8662	$113.87	$113.85	$113.90
Purchase #7	$6.62	12.732%	$7.4629	$7.46	$7.45	$7.50
7 purchase totals =	$967.02		$1,042.8634	$1,042.87	$1,042.85	$1,042.80