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	$111.82	13.220%	$126.6026	$126.60	$126.60	$126.60
Purchase #2	$202.57	3.759%	$210.1846	$210.18	$210.20	$210.20
Purchase #3	$49.86	12.410%	$56.0476	$56.05	$56.05	$56.00
Purchase #4	$115.38	10.228%	$127.1811	$127.18	$127.20	$127.20
Purchase #5	$186.69	9.165%	$203.8001	$203.80	$203.80	$203.80
Purchase #6	$38.60	5.490%	$40.7191	$40.72	$40.70	$40.70
Purchase #7	$156.53	7.574%	$168.3856	$168.39	$168.40	$168.40
7 purchase totals =	$861.45		$932.9207	$932.92	$932.95	$932.90