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	$38.93	6.743%	$41.555	$41.56	$41.55	$41.60
Purchase #2	$51.38	10.593%	$56.8227	$56.82	$56.80	$56.80
Purchase #3	$100.46	11.301%	$111.813	$111.81	$111.80	$111.80
Purchase #4	$35.43	4.665%	$37.0828	$37.08	$37.10	$37.10
Purchase #5	$80.48	11.450%	$89.695	$89.70	$89.70	$89.70
Purchase #6	$67.89	11.361%	$75.603	$75.60	$75.60	$75.60
Purchase #7	$138.81	13.652%	$157.7603	$157.76	$157.75	$157.80
7 purchase totals =	$513.38		$570.3318	$570.33	$570.30	$570.40