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	$113.50	12.566%	$127.7624	$127.76	$127.75	$127.80
Purchase #2	$72.94	7.315%	$78.2756	$78.28	$78.30	$78.30
Purchase #3	$108.42	7.288%	$116.3216	$116.32	$116.30	$116.30
Purchase #4	$40.87	6.330%	$43.4571	$43.46	$43.45	$43.50
Purchase #5	$215.72	12.341%	$242.342	$242.34	$242.35	$242.30
Purchase #6	$45.45	7.317%	$48.7756	$48.78	$48.80	$48.80
Purchase #7	$196.41	3.866%	$204.0032	$204.00	$204.00	$204.00
7 purchase totals =	$793.31		$860.9375	$860.94	$860.95	$861.00