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	$138.65	5.635%	$146.4629	$146.46	$146.45	$146.50
Purchase #2	$116.47	6.635%	$124.1978	$124.20	$124.20	$124.20
Purchase #3	$71.43	10.476%	$78.913	$78.91	$78.90	$78.90
Purchase #4	$174.95	7.492%	$188.0573	$188.06	$188.05	$188.10
Purchase #5	$167.87	4.398%	$175.2529	$175.25	$175.25	$175.30
Purchase #6	$137.27	11.223%	$152.6758	$152.68	$152.70	$152.70
Purchase #7	$25.34	9.862%	$27.839	$27.84	$27.85	$27.80
7 purchase totals =	$831.98		$893.3987	$893.40	$893.40	$893.50