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	$6.50	8.487%	$7.0517	$7.05	$7.05	$7.10
Purchase #2	$134.94	7.828%	$145.5031	$145.50	$145.50	$145.50
Purchase #3	$157.29	4.332%	$164.1038	$164.10	$164.10	$164.10
Purchase #4	$97.43	4.153%	$101.4763	$101.48	$101.50	$101.50
Purchase #5	$96.56	8.818%	$105.0747	$105.07	$105.05	$105.10
Purchase #6	$81.57	6.437%	$86.8207	$86.82	$86.80	$86.80
Purchase #7	$177.60	7.796%	$191.4457	$191.45	$191.45	$191.40
7 purchase totals =	$751.89		$801.4760	$801.47	$801.45	$801.50