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	$79.64	3.244%	$82.2235	$82.22	$82.20	$82.20
Purchase #2	$86.71	9.771%	$95.1824	$95.18	$95.20	$95.20
Purchase #3	$87.56	9.109%	$95.5358	$95.54	$95.55	$95.50
Purchase #4	$199.56	7.328%	$214.1838	$214.18	$214.20	$214.20
Purchase #5	$207.53	8.765%	$225.72	$225.72	$225.70	$225.70
Purchase #6	$12.94	5.330%	$13.6297	$13.63	$13.65	$13.60
Purchase #7	$94.95	5.625%	$100.2909	$100.29	$100.30	$100.30
7 purchase totals =	$768.89		$826.7661	$826.76	$826.80	$826.70