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	$136.35	6.828%	$145.66	$145.66	$145.65	$145.70
Purchase #2	$77.64	3.180%	$80.109	$80.11	$80.10	$80.10
Purchase #3	$144.53	8.587%	$156.9408	$156.94	$156.95	$156.90
Purchase #4	$99.81	12.152%	$111.9389	$111.94	$111.95	$111.90
Purchase #5	$98.83	6.714%	$105.4654	$105.47	$105.45	$105.50
Purchase #6	$249.79	4.748%	$261.65	$261.65	$261.65	$261.70
Purchase #7	$106.40	3.219%	$109.825	$109.83	$109.85	$109.80
7 purchase totals =	$913.35		$971.5891	$971.60	$971.60	$971.60