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	$141.81	8.515%	$153.8851	$153.89	$153.90	$153.90
Purchase #2	$59.36	13.643%	$67.4585	$67.46	$67.45	$67.50
Purchase #3	$80.51	12.825%	$90.8354	$90.84	$90.85	$90.80
Purchase #4	$124.68	6.859%	$133.2318	$133.23	$133.25	$133.20
Purchase #5	$32.42	11.390%	$36.1126	$36.11	$36.10	$36.10
Purchase #6	$186.65	5.119%	$196.2046	$196.20	$196.20	$196.20
Purchase #7	$50.75	9.587%	$55.6154	$55.62	$55.60	$55.60
7 purchase totals =	$676.18		$733.3434	$733.35	$733.35	$733.30