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	$155.90	3.606%	$161.5218	$161.52	$161.50	$161.50
Purchase #2	$123.41	6.168%	$131.0219	$131.02	$131.00	$131.00
Purchase #3	$13.67	5.637%	$14.4406	$14.44	$14.45	$14.40
Purchase #4	$245.25	6.661%	$261.5861	$261.59	$261.60	$261.60
Purchase #5	$240.47	12.608%	$270.7885	$270.79	$270.80	$270.80
Purchase #6	$149.89	3.604%	$155.292	$155.29	$155.30	$155.30
Purchase #7	$70.54	9.127%	$76.9782	$76.98	$77.00	$77.00
7 purchase totals =	$999.13		$1,071.6291	$1,071.63	$1,071.65	$1,071.60