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	$41.72	4.873%	$43.753	$43.75	$43.75	$43.80
Purchase #2	$104.72	8.784%	$113.9186	$113.92	$113.90	$113.90
Purchase #3	$91.94	7.701%	$99.0203	$99.02	$99.00	$99.00
Purchase #4	$126.77	11.389%	$141.2078	$141.21	$141.20	$141.20
Purchase #5	$162.44	11.758%	$181.5397	$181.54	$181.55	$181.50
Purchase #6	$106.51	5.363%	$112.2221	$112.22	$112.20	$112.20
Purchase #7	$223.27	8.463%	$242.1653	$242.17	$242.15	$242.20
7 purchase totals =	$857.37		$933.8268	$933.83	$933.75	$933.80