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	$242.56	7.799%	$261.4773	$261.48	$261.50	$261.50
Purchase #2	$54.40	12.852%	$61.3915	$61.39	$61.40	$61.40
Purchase #3	$87.82	9.872%	$96.4896	$96.49	$96.50	$96.50
Purchase #4	$203.34	5.213%	$213.9401	$213.94	$213.95	$213.90
Purchase #5	$175.65	11.843%	$196.4522	$196.45	$196.45	$196.50
Purchase #6	$78.81	8.758%	$85.7122	$85.71	$85.70	$85.70
Purchase #7	$100.54	8.836%	$109.4237	$109.42	$109.40	$109.40
7 purchase totals =	$943.12		$1,024.8866	$1,024.88	$1,024.90	$1,024.90