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	$59.60	7.713%	$64.1969	$64.20	$64.20	$64.20
Purchase #2	$59.70	7.867%	$64.3966	$64.40	$64.40	$64.40
Purchase #3	$37.42	13.613%	$42.514	$42.51	$42.50	$42.50
Purchase #4	$48.49	6.156%	$51.475	$51.48	$51.50	$51.50
Purchase #5	$26.46	5.446%	$27.901	$27.90	$27.90	$27.90
Purchase #6	$241.50	9.426%	$264.2638	$264.26	$264.25	$264.30
Purchase #7	$126.32	5.505%	$133.2739	$133.27	$133.25	$133.30
7 purchase totals =	$599.49		$648.0212	$648.02	$648.00	$648.10