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	$33.80	3.131%	$34.8583	$34.86	$34.85	$34.90
Purchase #2	$163.27	3.430%	$168.8702	$168.87	$168.85	$168.90
Purchase #3	$181.88	13.568%	$206.5575	$206.56	$206.55	$206.60
Purchase #4	$11.59	8.650%	$12.5925	$12.59	$12.60	$12.60
Purchase #5	$120.44	4.654%	$126.0453	$126.05	$126.05	$126.00
Purchase #6	$209.77	7.798%	$226.1279	$226.13	$226.15	$226.10
Purchase #7	$225.60	13.427%	$255.8913	$255.89	$255.90	$255.90
7 purchase totals =	$946.35		$1,030.9430	$1,030.95	$1,030.95	$1,031.00