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	$198.57	9.186%	$216.8106	$216.81	$216.80	$216.80
Purchase #2	$100.29	4.560%	$104.8632	$104.86	$104.85	$104.90
Purchase #3	$223.98	11.247%	$249.171	$249.17	$249.15	$249.20
Purchase #4	$46.57	12.566%	$52.422	$52.42	$52.40	$52.40
Purchase #5	$107.92	5.303%	$113.643	$113.64	$113.65	$113.60
Purchase #6	$246.93	4.437%	$257.8863	$257.89	$257.90	$257.90
Purchase #7	$55.54	6.749%	$59.2884	$59.29	$59.30	$59.30
7 purchase totals =	$979.80		$1,054.0845	$1,054.08	$1,054.05	$1,054.10