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	$41.88	5.665%	$44.2525	$44.25	$44.25	$44.30
Purchase #2	$87.47	10.338%	$96.5126	$96.51	$96.50	$96.50
Purchase #3	$72.31	13.289%	$81.9193	$81.92	$81.90	$81.90
Purchase #4	$148.98	10.674%	$164.8821	$164.88	$164.90	$164.90
Purchase #5	$166.81	5.604%	$176.158	$176.16	$176.15	$176.20
Purchase #6	$204.36	4.473%	$213.501	$213.50	$213.50	$213.50
Purchase #7	$123.75	6.259%	$131.4955	$131.50	$131.50	$131.50
7 purchase totals =	$845.56		$908.7210	$908.72	$908.70	$908.80