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	$67.87	6.282%	$72.1336	$72.13	$72.15	$72.10
Purchase #2	$20.63	10.306%	$22.7561	$22.76	$22.75	$22.80
Purchase #3	$231.87	4.270%	$241.7708	$241.77	$241.75	$241.80
Purchase #4	$104.50	6.588%	$111.3845	$111.38	$111.40	$111.40
Purchase #5	$77.96	4.620%	$81.5618	$81.56	$81.55	$81.60
Purchase #6	$207.89	4.395%	$217.0268	$217.03	$217.05	$217.00
Purchase #7	$138.85	13.654%	$157.8086	$157.81	$157.80	$157.80
7 purchase totals =	$849.57		$904.4422	$904.44	$904.45	$904.50