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	$191.95	4.527%	$200.6396	$200.64	$200.65	$200.60
Purchase #2	$214.93	10.872%	$238.2972	$238.30	$238.30	$238.30
Purchase #3	$174.40	10.390%	$192.5202	$192.52	$192.50	$192.50
Purchase #4	$207.31	3.190%	$213.9232	$213.92	$213.90	$213.90
Purchase #5	$54.80	7.742%	$59.0426	$59.04	$59.05	$59.00
Purchase #6	$132.75	6.311%	$141.1279	$141.13	$141.15	$141.10
Purchase #7	$90.46	4.197%	$94.2566	$94.26	$94.25	$94.30
7 purchase totals =	$1,066.60		$1,139.8073	$1,139.81	$1,139.80	$1,139.70