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	$129.94	9.661%	$142.4935	$142.49	$142.50	$142.50
Purchase #2	$40.89	7.439%	$43.9318	$43.93	$43.95	$43.90
Purchase #3	$174.41	8.851%	$189.847	$189.85	$189.85	$189.80
Purchase #4	$20.76	11.333%	$23.1127	$23.11	$23.10	$23.10
Purchase #5	$105.92	3.192%	$109.301	$109.30	$109.30	$109.30
Purchase #6	$137.43	6.671%	$146.598	$146.60	$146.60	$146.60
Purchase #7	$208.27	8.727%	$226.4457	$226.45	$226.45	$226.40
7 purchase totals =	$817.62		$881.7297	$881.73	$881.75	$881.60