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	$120.56	8.684%	$131.0294	$131.03	$131.05	$131.00
Purchase #2	$171.33	4.821%	$179.5898	$179.59	$179.60	$179.60
Purchase #3	$143.67	4.749%	$150.4929	$150.49	$150.50	$150.50
Purchase #4	$182.37	9.284%	$199.3012	$199.30	$199.30	$199.30
Purchase #5	$123.62	8.210%	$133.7692	$133.77	$133.75	$133.80
Purchase #6	$81.95	12.703%	$92.3601	$92.36	$92.35	$92.40
Purchase #7	$157.31	7.272%	$168.7496	$168.75	$168.75	$168.70
7 purchase totals =	$980.81		$1,055.2922	$1,055.29	$1,055.30	$1,055.30