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	$54.51	5.303%	$57.4007	$57.40	$57.40	$57.40
Purchase #2	$27.94	12.267%	$31.3674	$31.37	$31.35	$31.40
Purchase #3	$153.27	12.294%	$172.113	$172.11	$172.10	$172.10
Purchase #4	$217.69	5.584%	$229.8458	$229.85	$229.85	$229.80
Purchase #5	$197.40	13.238%	$223.5318	$223.53	$223.55	$223.50
Purchase #6	$102.59	10.649%	$113.5148	$113.51	$113.50	$113.50
Purchase #7	$170.37	4.676%	$178.3365	$178.34	$178.35	$178.30
7 purchase totals =	$923.77		$1,006.1100	$1,006.11	$1,006.10	$1,006.00