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	$208.77	10.712%	$231.1334	$231.13	$231.15	$231.10
Purchase #2	$131.37	7.507%	$141.2319	$141.23	$141.25	$141.20
Purchase #3	$86.53	7.238%	$92.793	$92.79	$92.80	$92.80
Purchase #4	$137.95	3.420%	$142.6679	$142.67	$142.65	$142.70
Purchase #5	$139.79	13.520%	$158.6896	$158.69	$158.70	$158.70
Purchase #6	$83.85	12.537%	$94.3623	$94.36	$94.35	$94.40
Purchase #7	$91.87	9.331%	$100.4424	$100.44	$100.45	$100.40
7 purchase totals =	$880.13		$961.3205	$961.31	$961.35	$961.30