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	$152.54	3.763%	$158.2801	$158.28	$158.30	$158.30
Purchase #2	$52.71	12.356%	$59.2228	$59.22	$59.20	$59.20
Purchase #3	$41.47	7.469%	$44.5674	$44.57	$44.55	$44.60
Purchase #4	$197.90	10.725%	$219.1248	$219.12	$219.10	$219.10
Purchase #5	$137.83	9.334%	$150.6951	$150.70	$150.70	$150.70
Purchase #6	$43.36	13.185%	$49.077	$49.08	$49.10	$49.10
Purchase #7	$23.29	5.319%	$24.5288	$24.53	$24.55	$24.50
7 purchase totals =	$649.10		$705.4960	$705.50	$705.50	$705.50