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	$190.86	4.783%	$199.9888	$199.99	$200.00	$200.00
Purchase #2	$74.53	3.391%	$77.0573	$77.06	$77.05	$77.10
Purchase #3	$194.35	3.177%	$200.5245	$200.52	$200.50	$200.50
Purchase #4	$94.39	11.807%	$105.5346	$105.53	$105.55	$105.50
Purchase #5	$41.43	7.486%	$44.5314	$44.53	$44.55	$44.50
Purchase #6	$250.99	7.790%	$270.5421	$270.54	$270.55	$270.50
Purchase #7	$56.76	10.806%	$62.8935	$62.89	$62.90	$62.90
7 purchase totals =	$903.31		$961.0722	$961.06	$961.10	$961.00