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	$129.44	10.436%	$142.9484	$142.95	$142.95	$142.90
Purchase #2	$99.71	10.139%	$109.8196	$109.82	$109.80	$109.80
Purchase #3	$33.25	8.529%	$36.0859	$36.09	$36.10	$36.10
Purchase #4	$110.26	8.661%	$119.8096	$119.81	$119.80	$119.80
Purchase #5	$168.88	6.399%	$179.6866	$179.69	$179.70	$179.70
Purchase #6	$174.54	12.555%	$196.4535	$196.45	$196.45	$196.50
Purchase #7	$128.50	3.853%	$133.4511	$133.45	$133.45	$133.50
7 purchase totals =	$844.58		$918.2547	$918.26	$918.25	$918.30