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	$240.45	9.354%	$262.9417	$262.94	$262.95	$262.90
Purchase #2	$31.56	11.756%	$35.2702	$35.27	$35.25	$35.30
Purchase #3	$124.57	7.393%	$133.7795	$133.78	$133.80	$133.80
Purchase #4	$228.36	6.127%	$242.3516	$242.35	$242.35	$242.40
Purchase #5	$79.71	3.615%	$82.5915	$82.59	$82.60	$82.60
Purchase #6	$136.44	11.528%	$152.1688	$152.17	$152.15	$152.20
Purchase #7	$141.85	11.274%	$157.8422	$157.84	$157.85	$157.80
7 purchase totals =	$982.94		$1,066.9455	$1,066.94	$1,066.95	$1,067.00