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	$91.65	5.828%	$96.9914	$96.99	$97.00	$97.00
Purchase #2	$101.94	9.862%	$111.9933	$111.99	$112.00	$112.00
Purchase #3	$47.71	10.790%	$52.8579	$52.86	$52.85	$52.90
Purchase #4	$122.69	7.382%	$131.747	$131.75	$131.75	$131.70
Purchase #5	$78.74	11.754%	$87.9951	$88.00	$88.00	$88.00
Purchase #6	$54.99	7.357%	$59.0356	$59.04	$59.05	$59.00
Purchase #7	$203.39	6.147%	$215.8924	$215.89	$215.90	$215.90
7 purchase totals =	$701.11		$756.5127	$756.52	$756.55	$756.50