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	$14.53	4.252%	$15.1478	$15.15	$15.15	$15.10
Purchase #2	$165.98	9.690%	$182.0635	$182.06	$182.05	$182.10
Purchase #3	$82.47	9.570%	$90.3624	$90.36	$90.35	$90.40
Purchase #4	$215.90	8.560%	$234.381	$234.38	$234.40	$234.40
Purchase #5	$228.88	9.286%	$250.1338	$250.13	$250.15	$250.10
Purchase #6	$102.49	10.208%	$112.9522	$112.95	$112.95	$113.00
Purchase #7	$148.91	13.377%	$168.8297	$168.83	$168.85	$168.80
7 purchase totals =	$959.16		$1,053.8704	$1,053.86	$1,053.90	$1,053.90