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	$249.33	4.166%	$259.7171	$259.72	$259.70	$259.70
Purchase #2	$198.86	6.752%	$212.287	$212.29	$212.30	$212.30
Purchase #3	$27.83	6.723%	$29.701	$29.70	$29.70	$29.70
Purchase #4	$170.51	11.715%	$190.4852	$190.49	$190.50	$190.50
Purchase #5	$106.87	8.563%	$116.0213	$116.02	$116.00	$116.00
Purchase #6	$185.81	5.780%	$196.5498	$196.55	$196.55	$196.50
Purchase #7	$87.97	8.706%	$95.6287	$95.63	$95.65	$95.60
7 purchase totals =	$1,027.18		$1,100.3901	$1,100.40	$1,100.40	$1,100.30