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	$229.25	3.861%	$238.1013	$238.10	$238.10	$238.10
Purchase #2	$151.95	10.726%	$168.2482	$168.25	$168.25	$168.20
Purchase #3	$189.98	5.552%	$200.5277	$200.53	$200.55	$200.50
Purchase #4	$90.46	10.868%	$100.2912	$100.29	$100.30	$100.30
Purchase #5	$163.85	6.623%	$174.7018	$174.70	$174.70	$174.70
Purchase #6	$171.39	4.334%	$178.818	$178.82	$178.80	$178.80
Purchase #7	$46.34	4.695%	$48.5157	$48.52	$48.50	$48.50
7 purchase totals =	$1,043.22		$1,109.2039	$1,109.21	$1,109.20	$1,109.10