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	$63.86	5.455%	$67.3436	$67.34	$67.35	$67.30
Purchase #2	$174.39	4.674%	$182.541	$182.54	$182.55	$182.50
Purchase #3	$120.43	5.466%	$127.0127	$127.01	$127.00	$127.00
Purchase #4	$49.94	13.478%	$56.6709	$56.67	$56.65	$56.70
Purchase #5	$36.25	11.820%	$40.5348	$40.53	$40.55	$40.50
Purchase #6	$139.96	11.763%	$156.4235	$156.42	$156.40	$156.40
Purchase #7	$183.55	10.741%	$203.2651	$203.27	$203.25	$203.30
7 purchase totals =	$768.38		$833.7916	$833.78	$833.75	$833.70