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	$238.43	10.838%	$264.271	$264.27	$264.25	$264.30
Purchase #2	$76.29	12.162%	$85.5684	$85.57	$85.55	$85.60
Purchase #3	$159.48	3.216%	$164.6089	$164.61	$164.60	$164.60
Purchase #4	$154.97	7.232%	$166.1774	$166.18	$166.20	$166.20
Purchase #5	$31.78	10.191%	$35.0187	$35.02	$35.00	$35.00
Purchase #6	$71.84	8.856%	$78.2022	$78.20	$78.20	$78.20
Purchase #7	$137.31	10.774%	$152.1038	$152.10	$152.10	$152.10
7 purchase totals =	$870.10		$945.9504	$945.95	$945.90	$946.00