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	$236.67	11.669%	$264.287	$264.29	$264.30	$264.30
Purchase #2	$156.36	10.284%	$172.4401	$172.44	$172.45	$172.40
Purchase #3	$27.71	4.692%	$29.0102	$29.01	$29.00	$29.00
Purchase #4	$43.45	12.522%	$48.8908	$48.89	$48.90	$48.90
Purchase #5	$214.34	3.584%	$222.0219	$222.02	$222.00	$222.00
Purchase #6	$100.25	9.167%	$109.4399	$109.44	$109.45	$109.40
Purchase #7	$120.81	3.834%	$125.4419	$125.44	$125.45	$125.40
7 purchase totals =	$899.59		$971.5318	$971.53	$971.55	$971.40