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	$177.77	12.187%	$199.4348	$199.43	$199.45	$199.40
Purchase #2	$55.38	13.193%	$62.6863	$62.69	$62.70	$62.70
Purchase #3	$59.59	5.533%	$62.8871	$62.89	$62.90	$62.90
Purchase #4	$214.41	13.639%	$243.6534	$243.65	$243.65	$243.70
Purchase #5	$86.28	3.197%	$89.0384	$89.04	$89.05	$89.00
Purchase #6	$229.67	4.317%	$239.5849	$239.58	$239.60	$239.60
Purchase #7	$174.76	4.248%	$182.1838	$182.18	$182.20	$182.20
7 purchase totals =	$997.86		$1,079.4687	$1,079.46	$1,079.55	$1,079.50