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	$231.47	6.187%	$245.791	$245.79	$245.80	$245.80
Purchase #2	$40.74	12.782%	$45.9474	$45.95	$45.95	$45.90
Purchase #3	$48.68	8.722%	$52.9259	$52.93	$52.95	$52.90
Purchase #4	$105.79	11.413%	$117.8638	$117.86	$117.85	$117.90
Purchase #5	$38.97	10.159%	$42.929	$42.93	$42.95	$42.90
Purchase #6	$110.55	3.620%	$114.5519	$114.55	$114.55	$114.60
Purchase #7	$86.36	3.115%	$89.0501	$89.05	$89.05	$89.10
7 purchase totals =	$662.56		$709.0591	$709.06	$709.10	$709.10