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	$201.72	11.854%	$225.6319	$225.63	$225.65	$225.60
Purchase #2	$91.37	10.850%	$101.2836	$101.28	$101.30	$101.30
Purchase #3	$103.45	10.857%	$114.6816	$114.68	$114.70	$114.70
Purchase #4	$221.28	9.769%	$242.8968	$242.90	$242.90	$242.90
Purchase #5	$26.37	3.798%	$27.3715	$27.37	$27.35	$27.40
Purchase #6	$112.84	12.575%	$127.0296	$127.03	$127.05	$127.00
Purchase #7	$213.48	11.761%	$238.5874	$238.59	$238.60	$238.60
7 purchase totals =	$970.51		$1,077.4824	$1,077.48	$1,077.55	$1,077.50