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	$127.63	9.321%	$139.5264	$139.53	$139.55	$139.50
Purchase #2	$81.48	9.637%	$89.3322	$89.33	$89.35	$89.30
Purchase #3	$94.81	6.330%	$100.8115	$100.81	$100.80	$100.80
Purchase #4	$148.28	10.618%	$164.0244	$164.02	$164.00	$164.00
Purchase #5	$119.41	10.542%	$131.9982	$132.00	$132.00	$132.00
Purchase #6	$133.58	3.472%	$138.2179	$138.22	$138.20	$138.20
Purchase #7	$241.33	12.834%	$272.3023	$272.30	$272.30	$272.30
7 purchase totals =	$946.52		$1,036.2129	$1,036.21	$1,036.20	$1,036.10