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	$217.31	8.274%	$235.2902	$235.29	$235.30	$235.30
Purchase #2	$28.70	3.140%	$29.6012	$29.60	$29.60	$29.60
Purchase #3	$28.61	13.161%	$32.3754	$32.38	$32.40	$32.40
Purchase #4	$245.61	10.287%	$270.8759	$270.88	$270.90	$270.90
Purchase #5	$23.25	4.231%	$24.2337	$24.23	$24.25	$24.20
Purchase #6	$92.38	4.500%	$96.5371	$96.54	$96.55	$96.50
Purchase #7	$234.57	3.827%	$243.547	$243.55	$243.55	$243.50
7 purchase totals =	$870.43		$932.4605	$932.47	$932.55	$932.40