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	$59.63	7.813%	$64.2889	$64.29	$64.30	$64.30
Purchase #2	$20.59	6.482%	$21.9246	$21.92	$21.90	$21.90
Purchase #3	$97.76	13.612%	$111.0671	$111.07	$111.05	$111.10
Purchase #4	$110.38	10.781%	$122.2801	$122.28	$122.30	$122.30
Purchase #5	$134.63	5.504%	$142.04	$142.04	$142.05	$142.00
Purchase #6	$119.35	7.308%	$128.0721	$128.07	$128.05	$128.10
Purchase #7	$179.81	10.222%	$198.1902	$198.19	$198.20	$198.20
7 purchase totals =	$722.15		$787.8630	$787.86	$787.85	$787.90