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	$82.65	5.713%	$87.3718	$87.37	$87.35	$87.40
Purchase #2	$225.76	3.343%	$233.3072	$233.31	$233.30	$233.30
Purchase #3	$164.89	9.546%	$180.6304	$180.63	$180.65	$180.60
Purchase #4	$153.29	9.251%	$167.4709	$167.47	$167.45	$167.50
Purchase #5	$58.43	11.146%	$64.9426	$64.94	$64.95	$64.90
Purchase #6	$205.48	12.675%	$231.5246	$231.52	$231.50	$231.50
Purchase #7	$57.42	8.438%	$62.2651	$62.27	$62.25	$62.30
7 purchase totals =	$947.92		$1,027.5126	$1,027.51	$1,027.45	$1,027.50