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	$203.77	10.393%	$224.9478	$224.95	$224.95	$224.90
Purchase #2	$176.50	10.433%	$194.9142	$194.91	$194.90	$194.90
Purchase #3	$80.79	10.445%	$89.2285	$89.23	$89.25	$89.20
Purchase #4	$137.59	6.702%	$146.8113	$146.81	$146.80	$146.80
Purchase #5	$215.99	4.388%	$225.4676	$225.47	$225.45	$225.50
Purchase #6	$113.73	13.349%	$128.9118	$128.91	$128.90	$128.90
Purchase #7	$133.45	13.357%	$151.2749	$151.27	$151.25	$151.30
7 purchase totals =	$1,061.82		$1,161.5561	$1,161.55	$1,161.50	$1,161.50