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	$216.32	10.189%	$238.3608	$238.36	$238.35	$238.40
Purchase #2	$176.73	12.308%	$198.4819	$198.48	$198.50	$198.50
Purchase #3	$48.95	12.127%	$54.8862	$54.89	$54.90	$54.90
Purchase #4	$27.96	4.562%	$29.2355	$29.24	$29.25	$29.20
Purchase #5	$186.27	4.718%	$195.0582	$195.06	$195.05	$195.10
Purchase #6	$229.76	13.691%	$261.2164	$261.22	$261.20	$261.20
Purchase #7	$77.92	5.497%	$82.2033	$82.20	$82.20	$82.20
7 purchase totals =	$963.91		$1,059.4423	$1,059.45	$1,059.45	$1,059.50