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	$203.54	7.296%	$218.3903	$218.39	$218.40	$218.40
Purchase #2	$242.59	13.534%	$275.4221	$275.42	$275.40	$275.40
Purchase #3	$12.53	3.493%	$12.9677	$12.97	$12.95	$13.00
Purchase #4	$63.87	12.194%	$71.6583	$71.66	$71.65	$71.70
Purchase #5	$29.78	12.315%	$33.4474	$33.45	$33.45	$33.40
Purchase #6	$148.89	13.266%	$168.6417	$168.64	$168.65	$168.60
Purchase #7	$77.64	3.339%	$80.2324	$80.23	$80.25	$80.20
7 purchase totals =	$778.84		$860.7599	$860.76	$860.75	$860.70