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	$95.85	5.369%	$100.9962	$101.00	$101.00	$101.00
Purchase #2	$142.94	5.277%	$150.4829	$150.48	$150.50	$150.50
Purchase #3	$116.60	13.735%	$132.615	$132.62	$132.60	$132.60
Purchase #4	$250.49	11.166%	$278.4597	$278.46	$278.45	$278.50
Purchase #5	$149.82	3.818%	$155.5401	$155.54	$155.55	$155.50
Purchase #6	$155.68	8.866%	$169.4826	$169.48	$169.50	$169.50
Purchase #7	$220.61	11.635%	$246.278	$246.28	$246.30	$246.30
7 purchase totals =	$1,131.99		$1,233.8545	$1,233.86	$1,233.90	$1,233.90