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	$133.89	5.566%	$141.3423	$141.34	$141.35	$141.30
Purchase #2	$24.99	11.464%	$27.8549	$27.85	$27.85	$27.90
Purchase #3	$196.74	10.354%	$217.1105	$217.11	$217.10	$217.10
Purchase #4	$196.85	5.417%	$207.5134	$207.51	$207.50	$207.50
Purchase #5	$207.54	11.670%	$231.7599	$231.76	$231.75	$231.80
Purchase #6	$150.45	11.605%	$167.9097	$167.91	$167.90	$167.90
Purchase #7	$163.87	9.237%	$179.0067	$179.01	$179.00	$179.00
7 purchase totals =	$1,074.33		$1,172.4974	$1,172.49	$1,172.45	$1,172.50