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	$172.72	13.531%	$196.0907	$196.09	$196.10	$196.10
Purchase #2	$50.38	3.647%	$52.2174	$52.22	$52.20	$52.20
Purchase #3	$145.98	13.288%	$165.3778	$165.38	$165.40	$165.40
Purchase #4	$138.25	10.782%	$153.1561	$153.16	$153.15	$153.20
Purchase #5	$63.33	13.541%	$71.9055	$71.91	$71.90	$71.90
Purchase #6	$189.33	5.261%	$199.2907	$199.29	$199.30	$199.30
Purchase #7	$101.81	5.638%	$107.55	$107.55	$107.55	$107.60
7 purchase totals =	$861.80		$945.5882	$945.60	$945.60	$945.70