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	$186.98	7.195%	$200.4332	$200.43	$200.45	$200.40
Purchase #2	$212.63	9.182%	$232.1537	$232.15	$232.15	$232.20
Purchase #3	$153.39	3.484%	$158.7341	$158.73	$158.75	$158.70
Purchase #4	$90.44	11.168%	$100.5403	$100.54	$100.55	$100.50
Purchase #5	$37.91	12.357%	$42.5945	$42.59	$42.60	$42.60
Purchase #6	$38.93	5.568%	$41.0976	$41.10	$41.10	$41.10
Purchase #7	$125.34	10.813%	$138.893	$138.89	$138.90	$138.90
7 purchase totals =	$845.62		$914.4464	$914.43	$914.50	$914.40