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	$103.32	4.856%	$108.3372	$108.34	$108.35	$108.30
Purchase #2	$55.63	10.192%	$61.2998	$61.30	$61.30	$61.30
Purchase #3	$133.97	12.246%	$150.376	$150.38	$150.40	$150.40
Purchase #4	$249.53	12.728%	$281.2902	$281.29	$281.30	$281.30
Purchase #5	$68.36	7.149%	$73.2471	$73.25	$73.25	$73.20
Purchase #6	$228.66	4.308%	$238.5107	$238.51	$238.50	$238.50
Purchase #7	$176.43	12.269%	$198.0762	$198.08	$198.10	$198.10
7 purchase totals =	$1,015.90		$1,111.1372	$1,111.15	$1,111.20	$1,111.10