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	$53.56	5.646%	$56.584	$56.58	$56.60	$56.60
Purchase #2	$182.42	7.736%	$196.532	$196.53	$196.55	$196.50
Purchase #3	$82.71	3.447%	$85.561	$85.56	$85.55	$85.60
Purchase #4	$164.45	11.808%	$183.8683	$183.87	$183.85	$183.90
Purchase #5	$199.89	4.431%	$208.7471	$208.75	$208.75	$208.70
Purchase #6	$243.56	12.732%	$274.5701	$274.57	$274.55	$274.60
Purchase #7	$174.66	8.731%	$189.9096	$189.91	$189.90	$189.90
7 purchase totals =	$1,101.25		$1,195.7721	$1,195.77	$1,195.75	$1,195.80