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	$57.45	8.752%	$62.478	$62.48	$62.50	$62.50
Purchase #2	$23.86	5.347%	$25.1358	$25.14	$25.15	$25.10
Purchase #3	$54.78	5.661%	$57.8811	$57.88	$57.90	$57.90
Purchase #4	$5.30	10.339%	$5.848	$5.85	$5.85	$5.80
Purchase #5	$111.98	6.132%	$118.8466	$118.85	$118.85	$118.80
Purchase #6	$152.96	8.282%	$165.6281	$165.63	$165.65	$165.60
Purchase #7	$165.87	8.874%	$180.5893	$180.59	$180.60	$180.60
7 purchase totals =	$572.20		$616.4069	$616.42	$616.50	$616.30