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	$234.29	10.678%	$259.3075	$259.31	$259.30	$259.30
Purchase #2	$246.97	12.504%	$277.8511	$277.85	$277.85	$277.90
Purchase #3	$64.70	9.256%	$70.6886	$70.69	$70.70	$70.70
Purchase #4	$178.82	13.129%	$202.2973	$202.30	$202.30	$202.30
Purchase #5	$57.61	3.368%	$59.5503	$59.55	$59.55	$59.60
Purchase #6	$100.45	13.428%	$113.9384	$113.94	$113.95	$113.90
Purchase #7	$114.29	11.442%	$127.3671	$127.37	$127.35	$127.40
7 purchase totals =	$997.13		$1,111.0003	$1,111.01	$1,111.00	$1,111.10