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	$240.64	13.352%	$272.7703	$272.77	$272.75	$272.80
Purchase #2	$205.32	13.732%	$233.5145	$233.51	$233.50	$233.50
Purchase #3	$16.42	9.710%	$18.0144	$18.01	$18.00	$18.00
Purchase #4	$232.89	3.735%	$241.5884	$241.59	$241.60	$241.60
Purchase #5	$100.95	10.484%	$111.5336	$111.53	$111.55	$111.50
Purchase #6	$145.56	9.445%	$159.3081	$159.31	$159.30	$159.30
Purchase #7	$104.91	9.874%	$115.2688	$115.27	$115.25	$115.30
7 purchase totals =	$1,046.69		$1,151.9981	$1,151.99	$1,151.95	$1,152.00