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	$144.91	9.649%	$158.8924	$158.89	$158.90	$158.90
Purchase #2	$101.71	13.377%	$115.3157	$115.32	$115.30	$115.30
Purchase #3	$71.49	9.279%	$78.1236	$78.12	$78.10	$78.10
Purchase #4	$203.71	11.295%	$226.719	$226.72	$226.70	$226.70
Purchase #5	$221.72	11.125%	$246.3864	$246.39	$246.40	$246.40
Purchase #6	$215.34	11.864%	$240.8879	$240.89	$240.90	$240.90
Purchase #7	$62.85	6.337%	$66.8328	$66.83	$66.85	$66.80
7 purchase totals =	$1,021.73		$1,133.1578	$1,133.16	$1,133.15	$1,133.10