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	$124.61	6.587%	$132.8181	$132.82	$132.80	$132.80
Purchase #2	$198.31	6.147%	$210.5001	$210.50	$210.50	$210.50
Purchase #3	$103.78	10.140%	$114.3033	$114.30	$114.30	$114.30
Purchase #4	$78.79	3.640%	$81.658	$81.66	$81.65	$81.70
Purchase #5	$225.62	6.140%	$239.4731	$239.47	$239.45	$239.50
Purchase #6	$131.67	4.301%	$137.3331	$137.33	$137.35	$137.30
Purchase #7	$83.39	7.744%	$89.8477	$89.85	$89.85	$89.80
7 purchase totals =	$946.17		$1,005.9334	$1,005.93	$1,005.90	$1,005.90