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	$152.90	8.622%	$166.083	$166.08	$166.10	$166.10
Purchase #2	$168.32	8.340%	$182.3579	$182.36	$182.35	$182.40
Purchase #3	$181.38	8.440%	$196.6885	$196.69	$196.70	$196.70
Purchase #4	$215.45	10.218%	$237.4647	$237.46	$237.45	$237.50
Purchase #5	$12.96	12.501%	$14.5801	$14.58	$14.60	$14.60
Purchase #6	$43.82	3.847%	$45.5058	$45.51	$45.50	$45.50
Purchase #7	$65.47	9.854%	$71.9214	$71.92	$71.90	$71.90
7 purchase totals =	$840.30		$914.6014	$914.60	$914.60	$914.70