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	$128.38	10.569%	$141.9485	$141.95	$141.95	$141.90
Purchase #2	$123.43	6.544%	$131.5073	$131.51	$131.50	$131.50
Purchase #3	$45.79	12.469%	$51.4996	$51.50	$51.50	$51.50
Purchase #4	$195.90	8.505%	$212.5613	$212.56	$212.55	$212.60
Purchase #5	$187.94	9.356%	$205.5237	$205.52	$205.50	$205.50
Purchase #6	$198.43	11.332%	$220.9161	$220.92	$220.90	$220.90
Purchase #7	$32.56	12.843%	$36.7417	$36.74	$36.75	$36.70
7 purchase totals =	$912.43		$1,000.6982	$1,000.70	$1,000.65	$1,000.60