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	$176.50	8.528%	$191.5519	$191.55	$191.55	$191.60
Purchase #2	$53.56	9.248%	$58.5132	$58.51	$58.50	$58.50
Purchase #3	$165.83	3.633%	$171.8546	$171.85	$171.85	$171.90
Purchase #4	$66.92	8.783%	$72.7976	$72.80	$72.80	$72.80
Purchase #5	$200.30	8.517%	$217.3596	$217.36	$217.35	$217.40
Purchase #6	$112.85	12.328%	$126.7621	$126.76	$126.75	$126.80
Purchase #7	$40.63	3.533%	$42.0655	$42.07	$42.05	$42.10
7 purchase totals =	$816.59		$880.9045	$880.90	$880.85	$881.10