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	$11.28	5.645%	$11.9168	$11.92	$11.90	$11.90
Purchase #2	$113.41	8.701%	$123.2778	$123.28	$123.30	$123.30
Purchase #3	$98.30	13.570%	$111.6393	$111.64	$111.65	$111.60
Purchase #4	$15.86	6.449%	$16.8828	$16.88	$16.90	$16.90
Purchase #5	$122.92	9.688%	$134.8285	$134.83	$134.85	$134.80
Purchase #6	$175.83	5.811%	$186.0475	$186.05	$186.05	$186.00
Purchase #7	$249.57	6.129%	$264.8661	$264.87	$264.85	$264.90
7 purchase totals =	$787.17		$849.4588	$849.47	$849.50	$849.40