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	$156.60	8.149%	$169.3613	$169.36	$169.35	$169.40
Purchase #2	$113.60	4.182%	$118.3508	$118.35	$118.35	$118.40
Purchase #3	$189.63	3.351%	$195.9845	$195.98	$196.00	$196.00
Purchase #4	$126.30	10.407%	$139.444	$139.44	$139.45	$139.40
Purchase #5	$201.44	6.517%	$214.5678	$214.57	$214.55	$214.60
Purchase #6	$39.31	7.184%	$42.134	$42.13	$42.15	$42.10
Purchase #7	$144.69	12.282%	$162.4608	$162.46	$162.45	$162.50
7 purchase totals =	$971.57		$1,042.3032	$1,042.29	$1,042.30	$1,042.40