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	$105.52	11.182%	$117.3192	$117.32	$117.30	$117.30
Purchase #2	$215.89	9.706%	$236.8443	$236.84	$236.85	$236.80
Purchase #3	$178.27	12.250%	$200.1081	$200.11	$200.10	$200.10
Purchase #4	$74.82	7.523%	$80.4487	$80.45	$80.45	$80.40
Purchase #5	$91.30	6.676%	$97.3952	$97.40	$97.40	$97.40
Purchase #6	$157.30	11.440%	$175.2951	$175.30	$175.30	$175.30
Purchase #7	$106.51	5.282%	$112.1359	$112.14	$112.15	$112.10
7 purchase totals =	$929.61		$1,019.5465	$1,019.56	$1,019.55	$1,019.40