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	$38.62	11.284%	$42.9779	$42.98	$43.00	$43.00
Purchase #2	$35.42	4.489%	$37.01	$37.01	$37.00	$37.00
Purchase #3	$5.82	13.866%	$6.627	$6.63	$6.65	$6.60
Purchase #4	$99.33	3.134%	$102.443	$102.44	$102.45	$102.40
Purchase #5	$164.70	12.421%	$185.1574	$185.16	$185.15	$185.20
Purchase #6	$178.77	3.590%	$185.1878	$185.19	$185.20	$185.20
Purchase #7	$197.27	13.555%	$224.0099	$224.01	$224.00	$224.00
7 purchase totals =	$719.93		$783.4130	$783.42	$783.45	$783.40