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	$118.34	12.125%	$132.6887	$132.69	$132.70	$132.70
Purchase #2	$178.63	3.586%	$185.0357	$185.04	$185.05	$185.00
Purchase #3	$223.71	6.814%	$238.9536	$238.95	$238.95	$239.00
Purchase #4	$105.60	5.494%	$111.4017	$111.40	$111.40	$111.40
Purchase #5	$232.50	12.737%	$262.1135	$262.11	$262.10	$262.10
Purchase #6	$41.63	10.321%	$45.9266	$45.93	$45.95	$45.90
Purchase #7	$23.46	8.789%	$25.5219	$25.52	$25.50	$25.50
7 purchase totals =	$923.87		$1,001.6417	$1,001.64	$1,001.65	$1,001.60