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	$176.50	6.835%	$188.5638	$188.56	$188.55	$188.60
Purchase #2	$118.29	5.740%	$125.0798	$125.08	$125.10	$125.10
Purchase #3	$210.87	5.670%	$222.8263	$222.83	$222.85	$222.80
Purchase #4	$163.38	5.264%	$171.9803	$171.98	$172.00	$172.00
Purchase #5	$157.35	6.713%	$167.9129	$167.91	$167.90	$167.90
Purchase #6	$108.85	13.870%	$123.9475	$123.95	$123.95	$123.90
Purchase #7	$27.77	13.278%	$31.4573	$31.46	$31.45	$31.50
7 purchase totals =	$963.01		$1,031.7679	$1,031.77	$1,031.80	$1,031.80