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	$34.32	4.736%	$35.9454	$35.95	$35.95	$35.90
Purchase #2	$239.85	7.695%	$258.3065	$258.31	$258.30	$258.30
Purchase #3	$72.50	11.205%	$80.6236	$80.62	$80.60	$80.60
Purchase #4	$146.69	12.176%	$164.551	$164.55	$164.55	$164.60
Purchase #5	$233.97	5.376%	$246.5482	$246.55	$246.55	$246.50
Purchase #6	$35.86	11.260%	$39.8978	$39.90	$39.90	$39.90
Purchase #7	$113.50	12.782%	$128.0076	$128.01	$128.00	$128.00
7 purchase totals =	$876.69		$953.8801	$953.89	$953.85	$953.80