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	$116.65	4.807%	$122.2574	$122.26	$122.25	$122.30
Purchase #2	$222.50	11.567%	$248.2366	$248.24	$248.25	$248.20
Purchase #3	$247.69	8.439%	$268.5926	$268.59	$268.60	$268.60
Purchase #4	$138.49	7.315%	$148.6205	$148.62	$148.60	$148.60
Purchase #5	$18.37	9.789%	$20.1682	$20.17	$20.15	$20.20
Purchase #6	$198.35	5.597%	$209.4516	$209.45	$209.45	$209.50
Purchase #7	$98.59	13.199%	$111.6029	$111.60	$111.60	$111.60
7 purchase totals =	$1,040.64		$1,128.9298	$1,128.93	$1,128.90	$1,129.00