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	$118.39	4.360%	$123.5518	$123.55	$123.55	$123.60
Purchase #2	$224.78	7.564%	$241.7824	$241.78	$241.80	$241.80
Purchase #3	$83.25	7.750%	$89.7019	$89.70	$89.70	$89.70
Purchase #4	$206.92	7.621%	$222.6894	$222.69	$222.70	$222.70
Purchase #5	$5.47	6.843%	$5.8443	$5.84	$5.85	$5.80
Purchase #6	$131.45	12.718%	$148.1678	$148.17	$148.15	$148.20
Purchase #7	$180.98	5.490%	$190.9158	$190.92	$190.90	$190.90
7 purchase totals =	$951.24		$1,022.6534	$1,022.65	$1,022.65	$1,022.70