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	$139.50	9.589%	$152.8767	$152.88	$152.90	$152.90
Purchase #2	$157.25	4.351%	$164.0919	$164.09	$164.10	$164.10
Purchase #3	$109.87	7.467%	$118.074	$118.07	$118.05	$118.10
Purchase #4	$119.47	7.666%	$128.6286	$128.63	$128.65	$128.60
Purchase #5	$99.91	13.160%	$113.0582	$113.06	$113.05	$113.10
Purchase #6	$59.61	13.649%	$67.7462	$67.75	$67.75	$67.70
Purchase #7	$38.80	10.830%	$43.002	$43.00	$43.00	$43.00
7 purchase totals =	$724.41		$787.4776	$787.48	$787.50	$787.50