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	$149.34	8.660%	$162.2728	$162.27	$162.25	$162.30
Purchase #2	$41.47	13.866%	$47.2202	$47.22	$47.20	$47.20
Purchase #3	$88.54	9.649%	$97.0832	$97.08	$97.10	$97.10
Purchase #4	$28.53	13.782%	$32.462	$32.46	$32.45	$32.50
Purchase #5	$67.83	13.691%	$77.1166	$77.12	$77.10	$77.10
Purchase #6	$30.76	12.342%	$34.5564	$34.56	$34.55	$34.60
Purchase #7	$119.31	3.868%	$123.9249	$123.92	$123.90	$123.90
7 purchase totals =	$525.78		$574.6361	$574.63	$574.55	$574.70