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	$208.82	10.169%	$230.0549	$230.05	$230.05	$230.10
Purchase #2	$180.90	10.300%	$199.5327	$199.53	$199.55	$199.50
Purchase #3	$93.30	6.659%	$99.5128	$99.51	$99.50	$99.50
Purchase #4	$248.93	7.310%	$267.1268	$267.13	$267.15	$267.10
Purchase #5	$131.61	7.235%	$141.132	$141.13	$141.15	$141.10
Purchase #6	$121.71	5.523%	$128.432	$128.43	$128.45	$128.40
Purchase #7	$233.80	10.149%	$257.5284	$257.53	$257.55	$257.50
7 purchase totals =	$1,219.07		$1,323.3196	$1,323.31	$1,323.40	$1,323.20