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	$120.69	10.594%	$133.4759	$133.48	$133.50	$133.50
Purchase #2	$101.29	13.387%	$114.8497	$114.85	$114.85	$114.80
Purchase #3	$27.48	3.566%	$28.4599	$28.46	$28.45	$28.50
Purchase #4	$187.28	4.605%	$195.9042	$195.90	$195.90	$195.90
Purchase #5	$173.56	13.475%	$196.9472	$196.95	$196.95	$196.90
Purchase #6	$167.78	8.573%	$182.1638	$182.16	$182.15	$182.20
Purchase #7	$95.27	7.229%	$102.1571	$102.16	$102.15	$102.20
7 purchase totals =	$873.35		$953.9578	$953.96	$953.95	$954.00