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	$127.34	9.205%	$139.0616	$139.06	$139.05	$139.10
Purchase #2	$156.61	9.299%	$171.1732	$171.17	$171.15	$171.20
Purchase #3	$157.31	11.763%	$175.8144	$175.81	$175.80	$175.80
Purchase #4	$67.65	10.265%	$74.5943	$74.59	$74.60	$74.60
Purchase #5	$48.33	5.785%	$51.1259	$51.13	$51.15	$51.10
Purchase #6	$85.95	12.273%	$96.4986	$96.50	$96.50	$96.50
Purchase #7	$140.50	8.296%	$152.1559	$152.16	$152.15	$152.20
7 purchase totals =	$783.69		$860.4239	$860.42	$860.40	$860.50