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	$184.77	6.827%	$197.3842	$197.38	$197.40	$197.40
Purchase #2	$142.39	8.497%	$154.4889	$154.49	$154.50	$154.50
Purchase #3	$34.65	11.288%	$38.5613	$38.56	$38.55	$38.60
Purchase #4	$109.63	6.263%	$116.4961	$116.50	$116.50	$116.50
Purchase #5	$142.98	6.298%	$151.9849	$151.98	$152.00	$152.00
Purchase #6	$100.91	12.438%	$113.4612	$113.46	$113.45	$113.50
Purchase #7	$196.74	13.329%	$222.9635	$222.96	$222.95	$223.00
7 purchase totals =	$912.07		$995.3401	$995.33	$995.35	$995.50