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	$180.49	8.675%	$196.1475	$196.15	$196.15	$196.10
Purchase #2	$154.66	12.594%	$174.1379	$174.14	$174.15	$174.10
Purchase #3	$128.29	4.592%	$134.1811	$134.18	$134.20	$134.20
Purchase #4	$84.70	5.700%	$89.5279	$89.53	$89.55	$89.50
Purchase #5	$58.36	6.334%	$62.0565	$62.06	$62.05	$62.10
Purchase #6	$148.29	10.579%	$163.9776	$163.98	$164.00	$164.00
Purchase #7	$157.26	13.397%	$178.3281	$178.33	$178.35	$178.30
7 purchase totals =	$912.05		$998.3566	$998.37	$998.45	$998.30