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	$71.52	13.471%	$81.1545	$81.15	$81.15	$81.20
Purchase #2	$77.86	13.661%	$88.4965	$88.50	$88.50	$88.50
Purchase #3	$51.51	10.253%	$56.7913	$56.79	$56.80	$56.80
Purchase #4	$29.86	11.742%	$33.3662	$33.37	$33.35	$33.40
Purchase #5	$49.37	3.245%	$50.9721	$50.97	$50.95	$51.00
Purchase #6	$59.80	10.781%	$66.247	$66.25	$66.25	$66.20
Purchase #7	$82.43	8.542%	$89.4712	$89.47	$89.45	$89.50
7 purchase totals =	$422.35		$466.4988	$466.50	$466.45	$466.60