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	$85.53	12.590%	$96.2982	$96.30	$96.30	$96.30
Purchase #2	$29.73	7.284%	$31.8955	$31.90	$31.90	$31.90
Purchase #3	$77.65	5.664%	$82.0481	$82.05	$82.05	$82.00
Purchase #4	$93.39	10.620%	$103.308	$103.31	$103.30	$103.30
Purchase #5	$22.35	8.207%	$24.1843	$24.18	$24.20	$24.20
Purchase #6	$80.68	5.860%	$85.4078	$85.41	$85.40	$85.40
Purchase #7	$172.45	13.835%	$196.3085	$196.31	$196.30	$196.30
7 purchase totals =	$561.78		$619.4504	$619.46	$619.45	$619.40