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	$114.61	7.471%	$123.1725	$123.17	$123.15	$123.20
Purchase #2	$177.61	11.142%	$197.3993	$197.40	$197.40	$197.40
Purchase #3	$125.55	12.801%	$141.6217	$141.62	$141.60	$141.60
Purchase #4	$85.96	4.537%	$89.86	$89.86	$89.85	$89.90
Purchase #5	$187.55	4.386%	$195.7759	$195.78	$195.80	$195.80
Purchase #6	$100.33	7.655%	$108.0103	$108.01	$108.00	$108.00
Purchase #7	$106.39	11.416%	$118.5355	$118.54	$118.55	$118.50
7 purchase totals =	$898.00		$974.3752	$974.38	$974.35	$974.40