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	$11.55	3.262%	$11.9268	$11.93	$11.95	$11.90
Purchase #2	$38.82	7.345%	$41.6713	$41.67	$41.65	$41.70
Purchase #3	$52.73	12.304%	$59.2179	$59.22	$59.20	$59.20
Purchase #4	$57.27	6.532%	$61.0109	$61.01	$61.00	$61.00
Purchase #5	$107.37	7.606%	$115.5366	$115.54	$115.55	$115.50
Purchase #6	$92.76	8.411%	$100.562	$100.56	$100.55	$100.60
Purchase #7	$203.83	12.583%	$229.4779	$229.48	$229.50	$229.50
7 purchase totals =	$564.33		$619.4034	$619.41	$619.40	$619.40