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	$32.43	10.310%	$35.7735	$35.77	$35.75	$35.80
Purchase #2	$42.44	9.314%	$46.3929	$46.39	$46.40	$46.40
Purchase #3	$66.45	10.450%	$73.394	$73.39	$73.40	$73.40
Purchase #4	$172.86	3.471%	$178.86	$178.86	$178.85	$178.90
Purchase #5	$89.98	11.149%	$100.0119	$100.01	$100.00	$100.00
Purchase #6	$242.76	12.868%	$273.9984	$274.00	$274.00	$274.00
Purchase #7	$200.32	8.780%	$217.9081	$217.91	$217.90	$217.90
7 purchase totals =	$847.24		$926.3388	$926.33	$926.30	$926.40