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	$246.42	7.232%	$264.2411	$264.24	$264.25	$264.20
Purchase #2	$133.56	11.484%	$148.898	$148.90	$148.90	$148.90
Purchase #3	$33.72	9.417%	$36.8954	$36.90	$36.90	$36.90
Purchase #4	$156.39	4.874%	$164.0124	$164.01	$164.00	$164.00
Purchase #5	$182.41	4.133%	$189.949	$189.95	$189.95	$189.90
Purchase #6	$138.78	9.480%	$151.9363	$151.94	$151.95	$151.90
Purchase #7	$102.67	9.245%	$112.1618	$112.16	$112.15	$112.20
7 purchase totals =	$993.95		$1,068.0940	$1,068.10	$1,068.10	$1,068.00