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	$213.41	5.638%	$225.4421	$225.44	$225.45	$225.40
Purchase #2	$90.55	4.623%	$94.7361	$94.74	$94.75	$94.70
Purchase #3	$156.69	11.194%	$174.2299	$174.23	$174.25	$174.20
Purchase #4	$179.67	9.390%	$196.541	$196.54	$196.55	$196.50
Purchase #5	$97.87	10.391%	$108.0397	$108.04	$108.05	$108.00
Purchase #6	$228.81	6.546%	$243.7879	$243.79	$243.80	$243.80
Purchase #7	$38.35	7.832%	$41.3536	$41.35	$41.35	$41.40
7 purchase totals =	$1,005.35		$1,084.1303	$1,084.13	$1,084.20	$1,084.00