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	$157.47	6.228%	$167.2772	$167.28	$167.30	$167.30
Purchase #2	$13.79	4.171%	$14.3652	$14.37	$14.35	$14.40
Purchase #3	$57.49	13.645%	$65.3345	$65.33	$65.35	$65.30
Purchase #4	$132.32	13.605%	$150.3221	$150.32	$150.30	$150.30
Purchase #5	$246.92	9.701%	$270.8737	$270.87	$270.85	$270.90
Purchase #6	$87.71	4.348%	$91.5236	$91.52	$91.50	$91.50
Purchase #7	$221.54	9.332%	$242.2141	$242.21	$242.20	$242.20
7 purchase totals =	$917.24		$1,001.9104	$1,001.90	$1,001.85	$1,001.90