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	$72.78	8.258%	$78.7902	$78.79	$78.80	$78.80
Purchase #2	$164.66	6.422%	$175.2345	$175.23	$175.25	$175.20
Purchase #3	$77.61	9.848%	$85.253	$85.25	$85.25	$85.30
Purchase #4	$224.71	12.402%	$252.5785	$252.58	$252.60	$252.60
Purchase #5	$59.29	11.857%	$66.32	$66.32	$66.30	$66.30
Purchase #6	$180.95	12.478%	$203.5289	$203.53	$203.55	$203.50
Purchase #7	$138.36	6.472%	$147.3147	$147.31	$147.30	$147.30
7 purchase totals =	$918.36		$1,009.0198	$1,009.01	$1,009.05	$1,009.00