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	$110.36	11.535%	$123.09	$123.09	$123.10	$123.10
Purchase #2	$152.30	3.364%	$157.4234	$157.42	$157.40	$157.40
Purchase #3	$155.54	5.664%	$164.3498	$164.35	$164.35	$164.30
Purchase #4	$245.59	11.324%	$273.4006	$273.40	$273.40	$273.40
Purchase #5	$120.60	8.207%	$130.4976	$130.50	$130.50	$130.50
Purchase #6	$49.92	13.121%	$56.47	$56.47	$56.45	$56.50
Purchase #7	$178.47	12.311%	$200.4414	$200.44	$200.45	$200.40
7 purchase totals =	$1,012.78		$1,105.6728	$1,105.67	$1,105.65	$1,105.60