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	$245.51	6.574%	$261.6498	$261.65	$261.65	$261.60
Purchase #2	$123.78	6.572%	$131.9148	$131.91	$131.90	$131.90
Purchase #3	$140.48	4.744%	$147.1444	$147.14	$147.15	$147.10
Purchase #4	$96.30	8.182%	$104.1793	$104.18	$104.20	$104.20
Purchase #5	$87.72	13.146%	$99.2517	$99.25	$99.25	$99.30
Purchase #6	$136.86	8.762%	$148.8517	$148.85	$148.85	$148.90
Purchase #7	$118.91	4.227%	$123.9363	$123.94	$123.95	$123.90
7 purchase totals =	$949.56		$1,016.9280	$1,016.92	$1,016.95	$1,016.90