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	$113.40	11.383%	$126.3083	$126.31	$126.30	$126.30
Purchase #2	$134.31	6.723%	$143.3397	$143.34	$143.35	$143.30
Purchase #3	$138.47	10.757%	$153.3652	$153.37	$153.35	$153.40
Purchase #4	$14.88	6.677%	$15.8735	$15.87	$15.85	$15.90
Purchase #5	$200.26	13.734%	$227.7637	$227.76	$227.75	$227.80
Purchase #6	$135.35	12.403%	$152.1375	$152.14	$152.15	$152.10
Purchase #7	$99.87	9.712%	$109.5694	$109.57	$109.55	$109.60
7 purchase totals =	$836.54		$928.3573	$928.36	$928.30	$928.40