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	$83.38	3.520%	$86.315	$86.32	$86.30	$86.30
Purchase #2	$38.79	4.351%	$40.4778	$40.48	$40.50	$40.50
Purchase #3	$157.33	4.844%	$164.9511	$164.95	$164.95	$165.00
Purchase #4	$105.91	9.868%	$116.3612	$116.36	$116.35	$116.40
Purchase #5	$32.98	9.709%	$36.182	$36.18	$36.20	$36.20
Purchase #6	$34.79	8.484%	$37.7416	$37.74	$37.75	$37.70
Purchase #7	$198.89	5.518%	$209.8648	$209.86	$209.85	$209.90
7 purchase totals =	$652.07		$691.8935	$691.89	$691.90	$692.00