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	$140.45	11.757%	$156.9627	$156.96	$156.95	$157.00
Purchase #2	$166.58	7.568%	$179.1868	$179.19	$179.20	$179.20
Purchase #3	$54.69	5.392%	$57.6389	$57.64	$57.65	$57.60
Purchase #4	$76.39	11.683%	$85.3146	$85.31	$85.30	$85.30
Purchase #5	$183.82	13.392%	$208.4372	$208.44	$208.45	$208.40
Purchase #6	$130.56	11.483%	$145.5522	$145.55	$145.55	$145.60
Purchase #7	$184.84	6.332%	$196.5441	$196.54	$196.55	$196.50
7 purchase totals =	$937.33		$1,029.6365	$1,029.63	$1,029.65	$1,029.60