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	$44.89	5.679%	$47.4393	$47.44	$47.45	$47.40
Purchase #2	$39.88	6.141%	$42.329	$42.33	$42.35	$42.30
Purchase #3	$246.90	3.568%	$255.7094	$255.71	$255.70	$255.70
Purchase #4	$245.32	11.228%	$272.8645	$272.86	$272.85	$272.90
Purchase #5	$224.64	3.693%	$232.936	$232.94	$232.95	$232.90
Purchase #6	$32.81	11.237%	$36.4969	$36.50	$36.50	$36.50
Purchase #7	$90.82	13.476%	$103.0589	$103.06	$103.05	$103.10
7 purchase totals =	$925.26		$990.8340	$990.84	$990.85	$990.80