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	$70.73	11.490%	$78.8569	$78.86	$78.85	$78.90
Purchase #2	$240.62	12.609%	$270.9598	$270.96	$270.95	$271.00
Purchase #3	$191.82	4.252%	$199.9762	$199.98	$200.00	$200.00
Purchase #4	$32.66	11.621%	$36.4554	$36.46	$36.45	$36.50
Purchase #5	$192.30	8.105%	$207.8859	$207.89	$207.90	$207.90
Purchase #6	$212.43	13.623%	$241.3693	$241.37	$241.35	$241.40
Purchase #7	$150.80	6.856%	$161.1388	$161.14	$161.15	$161.10
7 purchase totals =	$1,091.36		$1,196.6423	$1,196.66	$1,196.65	$1,196.80