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	$144.82	5.583%	$152.9053	$152.91	$152.90	$152.90
Purchase #2	$190.28	3.469%	$196.8808	$196.88	$196.90	$196.90
Purchase #3	$106.60	8.486%	$115.6461	$115.65	$115.65	$115.60
Purchase #4	$123.47	8.460%	$133.9156	$133.92	$133.90	$133.90
Purchase #5	$60.51	9.773%	$66.4236	$66.42	$66.40	$66.40
Purchase #6	$210.60	12.699%	$237.3441	$237.34	$237.35	$237.30
Purchase #7	$114.56	3.421%	$118.4791	$118.48	$118.50	$118.50
7 purchase totals =	$950.84		$1,021.5946	$1,021.60	$1,021.60	$1,021.50