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	$156.29	5.174%	$164.3764	$164.38	$164.40	$164.40
Purchase #2	$36.48	5.533%	$38.4984	$38.50	$38.50	$38.50
Purchase #3	$177.38	3.630%	$183.8189	$183.82	$183.80	$183.80
Purchase #4	$193.80	8.108%	$209.5133	$209.51	$209.50	$209.50
Purchase #5	$153.95	8.302%	$166.7309	$166.73	$166.75	$166.70
Purchase #6	$176.27	11.455%	$196.4617	$196.46	$196.45	$196.50
Purchase #7	$118.88	12.238%	$133.4285	$133.43	$133.45	$133.40
7 purchase totals =	$1,013.05		$1,092.8281	$1,092.83	$1,092.85	$1,092.80