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	$130.88	10.697%	$144.8802	$144.88	$144.90	$144.90
Purchase #2	$93.43	9.107%	$101.9387	$101.94	$101.95	$101.90
Purchase #3	$15.91	10.552%	$17.5888	$17.59	$17.60	$17.60
Purchase #4	$174.37	13.870%	$198.5551	$198.56	$198.55	$198.60
Purchase #5	$187.76	11.314%	$209.0032	$209.00	$209.00	$209.00
Purchase #6	$131.50	6.130%	$139.561	$139.56	$139.55	$139.60
Purchase #7	$134.50	3.416%	$139.0945	$139.09	$139.10	$139.10
7 purchase totals =	$868.35		$950.6215	$950.62	$950.65	$950.70