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	$248.95	8.411%	$269.8892	$269.89	$269.90	$269.90
Purchase #2	$118.36	8.675%	$128.6277	$128.63	$128.65	$128.60
Purchase #3	$224.89	13.700%	$255.6999	$255.70	$255.70	$255.70
Purchase #4	$155.99	7.713%	$168.0215	$168.02	$168.00	$168.00
Purchase #5	$45.56	3.723%	$47.2562	$47.26	$47.25	$47.30
Purchase #6	$104.77	9.354%	$114.5702	$114.57	$114.55	$114.60
Purchase #7	$78.26	6.556%	$83.3907	$83.39	$83.40	$83.40
7 purchase totals =	$976.78		$1,067.4554	$1,067.46	$1,067.45	$1,067.50