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	$178.89	6.124%	$189.8452	$189.85	$189.85	$189.80
Purchase #2	$110.94	6.527%	$118.1811	$118.18	$118.20	$118.20
Purchase #3	$37.61	8.503%	$40.808	$40.81	$40.80	$40.80
Purchase #4	$59.37	13.676%	$67.4894	$67.49	$67.50	$67.50
Purchase #5	$185.53	9.856%	$203.8158	$203.82	$203.80	$203.80
Purchase #6	$165.82	10.226%	$182.7768	$182.78	$182.80	$182.80
Purchase #7	$194.42	7.197%	$208.4124	$208.41	$208.40	$208.40
7 purchase totals =	$932.58		$1,011.3287	$1,011.34	$1,011.35	$1,011.30