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	$98.34	11.777%	$109.9215	$109.92	$109.90	$109.90
Purchase #2	$231.72	3.176%	$239.0794	$239.08	$239.10	$239.10
Purchase #3	$100.95	7.139%	$108.1568	$108.16	$108.15	$108.20
Purchase #4	$243.69	12.826%	$274.9457	$274.95	$274.95	$274.90
Purchase #5	$152.82	6.254%	$162.3774	$162.38	$162.40	$162.40
Purchase #6	$140.90	5.423%	$148.541	$148.54	$148.55	$148.50
Purchase #7	$9.28	12.724%	$10.4608	$10.46	$10.45	$10.50
7 purchase totals =	$977.70		$1,053.4826	$1,053.49	$1,053.50	$1,053.50