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	$246.69	10.186%	$271.8178	$271.82	$271.80	$271.80
Purchase #2	$87.73	13.701%	$99.7499	$99.75	$99.75	$99.70
Purchase #3	$197.77	8.712%	$214.9997	$215.00	$215.00	$215.00
Purchase #4	$82.53	9.798%	$90.6163	$90.62	$90.60	$90.60
Purchase #5	$157.35	7.308%	$168.8491	$168.85	$168.85	$168.80
Purchase #6	$158.71	10.623%	$175.5698	$175.57	$175.55	$175.60
Purchase #7	$104.73	4.587%	$109.534	$109.53	$109.55	$109.50
7 purchase totals =	$1,035.51		$1,131.1366	$1,131.14	$1,131.10	$1,131.00