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	$64.76	11.369%	$72.1226	$72.12	$72.10	$72.10
Purchase #2	$105.44	13.688%	$119.8726	$119.87	$119.85	$119.90
Purchase #3	$190.97	5.491%	$201.4562	$201.46	$201.45	$201.50
Purchase #4	$229.27	5.664%	$242.2559	$242.26	$242.25	$242.30
Purchase #5	$41.41	5.160%	$43.5468	$43.55	$43.55	$43.50
Purchase #6	$95.36	5.200%	$100.3187	$100.32	$100.30	$100.30
Purchase #7	$136.83	13.247%	$154.9559	$154.96	$154.95	$155.00
7 purchase totals =	$864.04		$934.5287	$934.54	$934.45	$934.60