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	$213.60	8.316%	$231.363	$231.36	$231.35	$231.40
Purchase #2	$79.72	12.624%	$89.7839	$89.78	$89.80	$89.80
Purchase #3	$119.63	6.342%	$127.2169	$127.22	$127.20	$127.20
Purchase #4	$39.58	3.551%	$40.9855	$40.99	$41.00	$41.00
Purchase #5	$237.69	5.561%	$250.9079	$250.91	$250.90	$250.90
Purchase #6	$113.71	7.140%	$121.8289	$121.83	$121.85	$121.80
Purchase #7	$151.98	13.549%	$172.5718	$172.57	$172.55	$172.60
7 purchase totals =	$955.91		$1,034.6579	$1,034.66	$1,034.65	$1,034.70